From f77f84a01acf45b8ae0f40ff5202c6ed67e702c2 Mon Sep 17 00:00:00 2001
From: Davis Vaughan <davis@posit.co>
Date: Fri, 23 Oct 2026 20:55:52 -0400
Subject: [PATCH] Accept titles for `axis` in the remaining one axis functions

---
 R/locate.R                       |  7 +++-
 R/names.R                        | 14 ++++++-
 R/rep.R                          |  7 +++-
 R/roll.R                         |  7 +++-
 R/slice.R                        |  7 +++-
 R/split.R                        |  7 +++-
 R/titles.R                       |  7 +++-
 R/unstack.R                      |  7 +++-
 man/rray-locate.Rd               |  7 +++-
 man/rray-rep.Rd                  |  7 +++-
 man/rray-roll.Rd                 |  7 +++-
 man/rray-titles.Rd               |  7 +++-
 man/rray_axis_names.Rd           |  7 +++-
 man/rray_set_axis_names.Rd       |  7 +++-
 man/rray_slice.Rd                |  7 +++-
 man/rray_split.Rd                |  7 +++-
 man/rray_unstack.Rd              |  7 +++-
 plans/title-as-axis.md           | 16 ++++----
 src/decl/locate-decl.h           |  2 +-
 src/globals.c                    |  8 ++++
 src/globals.h                    | 13 +++++++
 src/init.c                       |  2 +
 src/locate.c                     | 29 +++++++-------
 src/locate.h                     |  4 +-
 src/names.c                      | 57 +++++++++++++++++++--------
 src/names.h                      |  4 +-
 src/rep-each.c                   | 23 +++++++----
 src/rep-each.h                   |  2 +-
 src/roll-each.c                  | 29 +++++++++-----
 src/roll-each.h                  |  2 +-
 src/slice-axis.c                 | 66 ++++++++++++++++++++++++--------
 src/slice-axis.h                 |  4 +-
 src/split.c                      | 32 +++++++++-------
 src/split.h                      |  2 +-
 src/stack.c                      |  4 +-
 src/titles.c                     | 31 ++++++++++-----
 src/titles.h                     |  2 +-
 src/unstack.c                    | 20 ++++++----
 src/unstack.h                    |  2 +-
 tests/testthat/_snaps/locate.md  | 18 ++++++++-
 tests/testthat/_snaps/names.md   | 36 ++++++++++++++++-
 tests/testthat/_snaps/rep.md     |  8 ++++
 tests/testthat/_snaps/roll.md    | 10 ++++-
 tests/testthat/_snaps/slice.md   | 12 +++++-
 tests/testthat/_snaps/split.md   | 10 ++++-
 tests/testthat/_snaps/titles.md  | 16 ++++++++
 tests/testthat/_snaps/unstack.md | 10 ++++-
 tests/testthat/test-locate.R     | 18 +++++++++
 tests/testthat/test-names.R      | 30 +++++++++++++++
 tests/testthat/test-rep.R        |  9 +++++
 tests/testthat/test-roll.R       |  9 +++++
 tests/testthat/test-slice.R      | 36 +++++++++++++++++
 tests/testthat/test-split.R      |  9 +++++
 tests/testthat/test-titles.R     | 17 ++++++++
 tests/testthat/test-unstack.R    |  6 +++
 55 files changed, 595 insertions(+), 139 deletions(-)
 create mode 100644 src/globals.c
 create mode 100644 src/globals.h

diff --git a/R/locate.R b/R/locate.R
index 57abc0dd..49dd551f 100644
--- a/R/locate.R
+++ b/R/locate.R
@@ -34,7 +34,8 @@
 #'
 #' @param x An array.
 #'
-#' @param axis A single integer giving the axis to locate along.
+#' @param axis The axis to locate along, given
+#'   [by position or by title][faq-axes].
 #'
 #' @param na_rm If `TRUE`, missing values are skipped.
 #'
@@ -51,6 +52,10 @@
 #'
 #' # Position of the minimum going across the columns
 #' rray_locate_min(x, axis = 2L)
+#'
+#' # Position of the minimum going across the columns, by title
+#' y <- rray_set_titles(x, c("row", "col"))
+#' rray_locate_min(y, axis = "col")
 NULL
 
 #' @rdname rray-locate
diff --git a/R/names.R b/R/names.R
index d5771bbe..652272fb 100644
--- a/R/names.R
+++ b/R/names.R
@@ -37,7 +37,8 @@ rray_names <- function(x) {
 #'
 #' @param x An array.
 #'
-#' @param axis A single integer. The axis to get names for.
+#' @param axis The axis to get names for, given
+#'   [by position or by title][faq-axes].
 #'
 #' @returns
 #' A character vector of names, or `NULL` if that axis has no names.
@@ -49,6 +50,10 @@ rray_names <- function(x) {
 #' rray_axis_names(x, 1)
 #' rray_axis_names(x, 2)
 #'
+#' # By title
+#' y <- rray_set_titles(x, c("row", "col"))
+#' rray_axis_names(y, "col")
+#'
 #' rray_row_names(x)
 #' rray_column_names(x)
 rray_axis_names <- function(x, axis) {
@@ -105,7 +110,8 @@ rray_set_names <- function(x, names) {
 #'
 #' @param x An array.
 #'
-#' @param axis A single integer. The axis to set names for.
+#' @param axis The axis to set names for, given
+#'   [by position or by title][faq-axes].
 #'
 #' @param names A character vector of names for `axis`, the same length as
 #'   the dimension of `axis`. Can also be `NULL` to remove names from `axis`.
@@ -120,6 +126,10 @@ rray_set_names <- function(x, names) {
 #' rray_set_axis_names(x, 1, c("r1", "r2"))
 #' rray_set_axis_names(x, 2, c("c1", "c2", "c3"))
 #'
+#' # By title
+#' y <- rray_set_titles(x, c("row", "col"))
+#' rray_set_axis_names(y, "col", c("c1", "c2", "c3"))
+#'
 #' rray_set_row_names(x, c("r1", "r2"))
 #' rray_set_column_names(x, c("c1", "c2", "c3"))
 rray_set_axis_names <- function(x, axis, names) {
diff --git a/R/rep.R b/R/rep.R
index 15213037..57a142c4 100644
--- a/R/rep.R
+++ b/R/rep.R
@@ -31,7 +31,8 @@
 #'
 #' @param axes An integer vector of axes to repeat along.
 #'
-#' @param axis A single integer representing the axis to repeat along.
+#' @param axis The axis to repeat along, given
+#'   [by position or by title][faq-axes].
 #'
 #' @returns
 #' An array with the same dimensions as `x`, except along the repeated axes.
@@ -58,6 +59,10 @@
 #' # A different number of repeats per row
 #' rray_rep_each(x, times = c(1, 2, 3), axis = 1)
 #'
+#' # A different number of repeats per row, by title
+#' z <- rray_set_titles(x, c("row", "col"))
+#' rray_rep_each(z, times = c(1, 2, 3), axis = "row")
+#'
 #' # Zeroes drop slices entirely
 #' rray_rep_each(x, times = c(1, 0, 2), axis = 1)
 #'
diff --git a/R/roll.R b/R/roll.R
index 9809231a..be729a58 100644
--- a/R/roll.R
+++ b/R/roll.R
@@ -226,7 +226,8 @@
 #'
 #' @param axes An integer vector of axes to roll along.
 #'
-#' @param axis A single integer representing the axis to roll along.
+#' @param axis The axis to roll along, given
+#'   [by position or by title][faq-axes].
 #'
 #' @returns
 #' An array with the same type and dimensions as `x`.
@@ -261,6 +262,10 @@
 #' # Roll each row by its own `n`, given as a one column matrix
 #' rray_roll_each(y, n = matrix(c(1, 0, -1), ncol = 1), axis = 2)
 #'
+#' # Roll each row by its own `n`, by title
+#' z <- rray_set_titles(y, c("row", "col"))
+#' rray_roll_each(z, n = matrix(c(1, 0, -1), ncol = 1), axis = "col")
+#'
 #' # Roll each column by its own `n`, given as a one row matrix
 #' rray_roll_each(y, n = matrix(c(0, 1, 2, 3), nrow = 1), axis = 1)
 #'
diff --git a/R/slice.R b/R/slice.R
index becba2a4..91aa71a0 100644
--- a/R/slice.R
+++ b/R/slice.R
@@ -58,7 +58,8 @@
 #' @param i A subscript for the selected axis. It takes any of the forms
 #'   allowed in `...`.
 #'
-#' @param axis A single integer. The axis to slice along.
+#' @param axis The axis to slice along, given
+#'   [by position or by title][faq-axes].
 #'
 #' @param value An array to assign to the selected positions. It is cast to
 #'   the type of `x`, then broadcast to the dimensions of the selection.
@@ -100,6 +101,10 @@
 #' rray_slice_rows(y, c("b", "a"))
 #' rray_slice_columns(x, -2)
 #'
+#' # Slice a single axis, by title
+#' z <- rray_set_titles(y, c("row", "col"))
+#' rray_slice_axis(z, c("e", "c"), axis = "col")
+#'
 #' # Assign one value to every first row
 #' rray_slice_assign(x, 1, TRUE, TRUE, value = 0L)
 #' rray_slice_assign_rows(x, 1, 0L)
diff --git a/R/split.R b/R/split.R
index 97a87998..31cec7a3 100644
--- a/R/split.R
+++ b/R/split.R
@@ -9,7 +9,8 @@
 #'
 #' @param x An array.
 #'
-#' @param axis A single integer representing the axis to split on.
+#' @param axis The axis to split along, given
+#'   [by position or by title][faq-axes].
 #'
 #' @param dimensions One of:
 #'
@@ -35,6 +36,10 @@
 #' # One array per column
 #' rray_split(x, axis = 2, dimensions = 1)
 #'
+#' # One array per column, by title
+#' y <- rray_set_titles(x, c("row", "col"))
+#' rray_split(y, axis = "col", dimensions = 1)
+#'
 #' # Arrays of dimension zero are allowed in the explicit form
 #' rray_split(x, axis = 2, dimensions = c(0, 2))
 #'
diff --git a/R/titles.R b/R/titles.R
index ffce5dfe..0909197a 100644
--- a/R/titles.R
+++ b/R/titles.R
@@ -14,7 +14,11 @@
 #'
 #' @param x An array.
 #'
-#' @param axis A single integer. The axis to get or set the title for.
+#' @param axis The axis to get or set the title for.
+#'
+#'   - For `rray_set_axis_title()`, given [by position or by title][faq-axes].
+#'
+#'   - For `rray_axis_title()`, given [by position][faq-axes].
 #'
 #' @param titles A character vector with one title per axis, or `NULL` to
 #'   remove all titles.
@@ -38,6 +42,7 @@
 #' rray_titles(x)
 #' rray_axis_title(x, 2)
 #' rray_set_axis_title(x, 1, NULL)
+#' rray_set_axis_title(x, "Row", "R")
 NULL
 
 #' @rdname rray-titles
diff --git a/R/unstack.R b/R/unstack.R
index 761a4e89..44c6c322 100644
--- a/R/unstack.R
+++ b/R/unstack.R
@@ -18,7 +18,8 @@
 #'
 #' @param x An array.
 #'
-#' @param axis A single integer representing the axis to unstack along.
+#' @param axis The axis to unstack along, given
+#'   [by position or by title][faq-axes].
 #'
 #' @returns
 #' A list of arrays with the same dimensions as `x`, except that `axis` has
@@ -36,6 +37,10 @@
 #' # One array per column
 #' rray_unstack(x, axis = 2)
 #'
+#' # One array per column, by title
+#' z <- rray_set_titles(x, c("row", "col"))
+#' rray_unstack(z, axis = "col")
+#'
 #' # Names along the axis become list names
 #' y <- array(1:4, c(2, 2), dimnames = list(c("a", "b"), c("x", "y")))
 #' rray_unstack(y, axis = 2)
diff --git a/man/rray-locate.Rd b/man/rray-locate.Rd
index e134c095..4161ab4c 100644
--- a/man/rray-locate.Rd
+++ b/man/rray-locate.Rd
@@ -15,7 +15,8 @@ rray_locate_min(x, ..., axis, na_rm = FALSE)
 
 \item{...}{These dots are for future extensions and must be empty.}
 
-\item{axis}{A single integer giving the axis to locate along.}
+\item{axis}{The axis to locate along, given
+\link[=faq-axes]{by position or by title}.}
 
 \item{na_rm}{If \code{TRUE}, missing values are skipped.}
 }
@@ -59,4 +60,8 @@ rray_locate_max(x, axis = 1L)
 
 # Position of the minimum going across the columns
 rray_locate_min(x, axis = 2L)
+
+# Position of the minimum going across the columns, by title
+y <- rray_set_titles(x, c("row", "col"))
+rray_locate_min(y, axis = "col")
 }
diff --git a/man/rray-rep.Rd b/man/rray-rep.Rd
index f06d728e..3167aff0 100644
--- a/man/rray-rep.Rd
+++ b/man/rray-rep.Rd
@@ -23,7 +23,8 @@ For \code{rray_rep_each()}, a vector of integers greater than or equal to
 
 \item{axes}{An integer vector of axes to repeat along.}
 
-\item{axis}{A single integer representing the axis to repeat along.}
+\item{axis}{The axis to repeat along, given
+\link[=faq-axes]{by position or by title}.}
 }
 \value{
 An array with the same dimensions as \code{x}, except along the repeated axes.
@@ -69,6 +70,10 @@ rray_rep(x, times = c(2, 3), axes = c(1, 2))
 # A different number of repeats per row
 rray_rep_each(x, times = c(1, 2, 3), axis = 1)
 
+# A different number of repeats per row, by title
+z <- rray_set_titles(x, c("row", "col"))
+rray_rep_each(z, times = c(1, 2, 3), axis = "row")
+
 # Zeroes drop slices entirely
 rray_rep_each(x, times = c(1, 0, 2), axis = 1)
 
diff --git a/man/rray-roll.Rd b/man/rray-roll.Rd
index d2a650bd..7fe5a939 100644
--- a/man/rray-roll.Rd
+++ b/man/rray-roll.Rd
@@ -24,7 +24,8 @@ dimensions of \code{x} with \code{axis} set to 1.}
 
 \item{axes}{An integer vector of axes to roll along.}
 
-\item{axis}{A single integer representing the axis to roll along.}
+\item{axis}{The axis to roll along, given
+\link[=faq-axes]{by position or by title}.}
 }
 \value{
 An array with the same type and dimensions as \code{x}.
@@ -269,6 +270,10 @@ y <- matrix(1:12, nrow = 3, byrow = TRUE)
 # Roll each row by its own `n`, given as a one column matrix
 rray_roll_each(y, n = matrix(c(1, 0, -1), ncol = 1), axis = 2)
 
+# Roll each row by its own `n`, by title
+z <- rray_set_titles(y, c("row", "col"))
+rray_roll_each(z, n = matrix(c(1, 0, -1), ncol = 1), axis = "col")
+
 # Roll each column by its own `n`, given as a one row matrix
 rray_roll_each(y, n = matrix(c(0, 1, 2, 3), nrow = 1), axis = 1)
 
diff --git a/man/rray-titles.Rd b/man/rray-titles.Rd
index 64d6f93d..12258b71 100644
--- a/man/rray-titles.Rd
+++ b/man/rray-titles.Rd
@@ -19,7 +19,11 @@ rray_set_axis_title(x, axis, title)
 \arguments{
 \item{x}{An array.}
 
-\item{axis}{A single integer. The axis to get or set the title for.}
+\item{axis}{The axis to get or set the title for.
+\itemize{
+\item For \code{rray_set_axis_title()}, given \link[=faq-axes]{by position or by title}.
+\item For \code{rray_axis_title()}, given \link[=faq-axes]{by position}.
+}}
 
 \item{titles}{A character vector with one title per axis, or \code{NULL} to
 remove all titles.}
@@ -54,4 +58,5 @@ x <- rray_set_titles(x, c("Row", "Column"))
 rray_titles(x)
 rray_axis_title(x, 2)
 rray_set_axis_title(x, 1, NULL)
+rray_set_axis_title(x, "Row", "R")
 }
diff --git a/man/rray_axis_names.Rd b/man/rray_axis_names.Rd
index 3121bf75..e91a7e67 100644
--- a/man/rray_axis_names.Rd
+++ b/man/rray_axis_names.Rd
@@ -15,7 +15,8 @@ rray_column_names(x)
 \arguments{
 \item{x}{An array.}
 
-\item{axis}{A single integer. The axis to get names for.}
+\item{axis}{The axis to get names for, given
+\link[=faq-axes]{by position or by title}.}
 }
 \value{
 A character vector of names, or \code{NULL} if that axis has no names.
@@ -34,6 +35,10 @@ x <- array(1:6, c(2, 3), dimnames = list(c("r1", "r2"), c("c1", "c2", "c3")))
 rray_axis_names(x, 1)
 rray_axis_names(x, 2)
 
+# By title
+y <- rray_set_titles(x, c("row", "col"))
+rray_axis_names(y, "col")
+
 rray_row_names(x)
 rray_column_names(x)
 }
diff --git a/man/rray_set_axis_names.Rd b/man/rray_set_axis_names.Rd
index 507b4861..6c82908b 100644
--- a/man/rray_set_axis_names.Rd
+++ b/man/rray_set_axis_names.Rd
@@ -15,7 +15,8 @@ rray_set_column_names(x, names)
 \arguments{
 \item{x}{An array.}
 
-\item{axis}{A single integer. The axis to set names for.}
+\item{axis}{The axis to set names for, given
+\link[=faq-axes]{by position or by title}.}
 
 \item{names}{A character vector of names for \code{axis}, the same length as
 the dimension of \code{axis}. Can also be \code{NULL} to remove names from \code{axis}.}
@@ -37,6 +38,10 @@ x <- array(1:6, c(2, 3))
 rray_set_axis_names(x, 1, c("r1", "r2"))
 rray_set_axis_names(x, 2, c("c1", "c2", "c3"))
 
+# By title
+y <- rray_set_titles(x, c("row", "col"))
+rray_set_axis_names(y, "col", c("c1", "c2", "c3"))
+
 rray_set_row_names(x, c("r1", "r2"))
 rray_set_column_names(x, c("c1", "c2", "c3"))
 }
diff --git a/man/rray_slice.Rd b/man/rray_slice.Rd
index b1fd1549..03f6b720 100644
--- a/man/rray_slice.Rd
+++ b/man/rray_slice.Rd
@@ -48,7 +48,8 @@ empty.}
 \item{i}{A subscript for the selected axis. It takes any of the forms
 allowed in \code{...}.}
 
-\item{axis}{A single integer. The axis to slice along.}
+\item{axis}{The axis to slice along, given
+\link[=faq-axes]{by position or by title}.}
 
 \item{value}{An array to assign to the selected positions. It is cast to
 the type of \code{x}, then broadcast to the dimensions of the selection.}
@@ -124,6 +125,10 @@ rray_slice_axis(x, c(4, 1), axis = 3)
 rray_slice_rows(y, c("b", "a"))
 rray_slice_columns(x, -2)
 
+# Slice a single axis, by title
+z <- rray_set_titles(y, c("row", "col"))
+rray_slice_axis(z, c("e", "c"), axis = "col")
+
 # Assign one value to every first row
 rray_slice_assign(x, 1, TRUE, TRUE, value = 0L)
 rray_slice_assign_rows(x, 1, 0L)
diff --git a/man/rray_split.Rd b/man/rray_split.Rd
index edcaa6af..dac0d6bc 100644
--- a/man/rray_split.Rd
+++ b/man/rray_split.Rd
@@ -11,7 +11,8 @@ rray_split(x, ..., axis, dimensions)
 
 \item{...}{These dots are for future extensions and must be empty.}
 
-\item{axis}{A single integer representing the axis to split on.}
+\item{axis}{The axis to split along, given
+\link[=faq-axes]{by position or by title}.}
 
 \item{dimensions}{One of:
 \itemize{
@@ -41,6 +42,10 @@ rray_split(x, axis = 1, dimensions = c(1, 5))
 # One array per column
 rray_split(x, axis = 2, dimensions = 1)
 
+# One array per column, by title
+y <- rray_set_titles(x, c("row", "col"))
+rray_split(y, axis = "col", dimensions = 1)
+
 # Arrays of dimension zero are allowed in the explicit form
 rray_split(x, axis = 2, dimensions = c(0, 2))
 
diff --git a/man/rray_unstack.Rd b/man/rray_unstack.Rd
index 773a35f6..c55030a2 100644
--- a/man/rray_unstack.Rd
+++ b/man/rray_unstack.Rd
@@ -11,7 +11,8 @@ rray_unstack(x, ..., axis)
 
 \item{...}{These dots are for future extensions and must be empty.}
 
-\item{axis}{A single integer representing the axis to unstack along.}
+\item{axis}{The axis to unstack along, given
+\link[=faq-axes]{by position or by title}.}
 }
 \value{
 A list of arrays with the same dimensions as \code{x}, except that \code{axis} has
@@ -40,6 +41,10 @@ rray_unstack(x, axis = 1)
 # One array per column
 rray_unstack(x, axis = 2)
 
+# One array per column, by title
+z <- rray_set_titles(x, c("row", "col"))
+rray_unstack(z, axis = "col")
+
 # Names along the axis become list names
 y <- array(1:4, c(2, 2), dimnames = list(c("a", "b"), c("x", "y")))
 rray_unstack(y, axis = 2)
diff --git a/plans/title-as-axis.md b/plans/title-as-axis.md
index 9b6324c8..ea85320f 100644
--- a/plans/title-as-axis.md
+++ b/plans/title-as-axis.md
@@ -574,21 +574,21 @@ Each top level item is one PR. Each PR runs `clang-format`, `air format .`,
 
   - [x] Add `faq-axes` and update the reduce and cumulative docs.
 
-- [ ] PR 3: Titles for one axis functions.
+- [x] PR 3: Titles for one axis functions.
 
-  - [ ] Locate.
+  - [x] Locate.
 
-  - [ ] Rep each and roll each.
+  - [x] Rep each and roll each.
 
-  - [ ] Slice axis and slice assign axis.
+  - [x] Slice axis and slice assign axis.
 
-  - [ ] Split and unstack.
+  - [x] Split and unstack.
 
-  - [ ] Names: `rray_axis_names()`, `rray_set_axis_names()`.
+  - [x] Names: `rray_axis_names()`, `rray_set_axis_names()`.
 
-  - [ ] Titles: `rray_set_axis_title()`.
+  - [x] Titles: `rray_set_axis_title()`.
 
-  - [ ] Docs for each.
+  - [x] Docs for each.
 
 - [ ] PR 4: Titles for multi axis functions.
 
diff --git a/src/decl/locate-decl.h b/src/decl/locate-decl.h
index 6f4b943f..1c745661 100644
--- a/src/decl/locate-decl.h
+++ b/src/decl/locate-decl.h
@@ -1,6 +1,6 @@
 static r_obj* rray_locate(
   r_obj* x,
-  int axis,
+  r_obj* axis,
   bool na_rm,
   enum rray_locate_op op,
   struct rray_arg* arg,
diff --git a/src/globals.c b/src/globals.c
new file mode 100644
index 00000000..0cafaf4b
--- /dev/null
+++ b/src/globals.c
@@ -0,0 +1,8 @@
+#include "globals.h"
+
+struct rray_globals rray_globals;
+
+void rray_init_globals(r_obj* ns) {
+  r_preserve_global(rray_globals.one_int = r_int(1));
+  r_preserve_global(rray_globals.two_int = r_int(2));
+}
diff --git a/src/globals.h b/src/globals.h
new file mode 100644
index 00000000..88bb15f2
--- /dev/null
+++ b/src/globals.h
@@ -0,0 +1,13 @@
+#ifndef RRAY_GLOBALS_H
+#define RRAY_GLOBALS_H
+
+#include "rlang.h"
+
+struct rray_globals {
+  r_obj* one_int;
+  r_obj* two_int;
+};
+
+extern struct rray_globals rray_globals;
+
+#endif
diff --git a/src/init.c b/src/init.c
index ccfab598..ccf6b7d0 100644
--- a/src/init.c
+++ b/src/init.c
@@ -510,10 +510,12 @@ void R_init_rray(DllInfo* dll) {
 }
 
 extern void rray_init_args(r_obj* ns);
+extern void rray_init_globals(r_obj* ns);
 extern void rray_init_syms(r_obj* ns);
 
 r_obj* ffi_rray_init_library(r_obj* ffi_ns) {
   r_init_library(ffi_ns);
+  rray_init_globals(ffi_ns);
   rray_init_syms(ffi_ns);
   rray_init_args(ffi_ns);
   return r_null;
diff --git a/src/locate.c b/src/locate.c
index af634a6e..5c4141d8 100644
--- a/src/locate.c
+++ b/src/locate.c
@@ -11,6 +11,7 @@
 #include "size.h"
 #include "strided-iterator.h"
 #include "strides.h"
+#include "titles.h"
 #include "type.h"
 #include "utils.h"
 
@@ -37,14 +38,13 @@ r_obj* ffi_rray_locate_max(
   r_obj* ffi_frame
 ) {
   struct r_lazy error_call = {.x = ffi_frame, .env = r_null};
-  const int axis = arg_as_int(ffi_axis, rray_args.axis, error_call);
   const bool na_rm = r_arg_as_bool(ffi_na_rm, "na_rm");
-  return rray_locate_max(ffi_x, axis, na_rm, rray_args.x, error_call);
+  return rray_locate_max(ffi_x, ffi_axis, na_rm, rray_args.x, error_call);
 }
 
 r_obj* rray_locate_max(
   r_obj* x,
-  int axis,
+  r_obj* axis,
   bool na_rm,
   struct rray_arg* arg,
   struct r_lazy error_call
@@ -59,14 +59,13 @@ r_obj* ffi_rray_locate_min(
   r_obj* ffi_frame
 ) {
   struct r_lazy error_call = {.x = ffi_frame, .env = r_null};
-  const int axis = arg_as_int(ffi_axis, rray_args.axis, error_call);
   const bool na_rm = r_arg_as_bool(ffi_na_rm, "na_rm");
-  return rray_locate_min(ffi_x, axis, na_rm, rray_args.x, error_call);
+  return rray_locate_min(ffi_x, ffi_axis, na_rm, rray_args.x, error_call);
 }
 
 r_obj* rray_locate_min(
   r_obj* x,
-  int axis,
+  r_obj* axis,
   bool na_rm,
   struct rray_arg* arg,
   struct r_lazy error_call
@@ -76,7 +75,7 @@ r_obj* rray_locate_min(
 
 static r_obj* rray_locate(
   r_obj* x,
-  int axis,
+  r_obj* axis,
   bool na_rm,
   enum rray_locate_op op,
   struct rray_arg* arg,
@@ -91,28 +90,32 @@ static r_obj* rray_locate(
   const int dimensionality = rray_dimensionality_from_dimensions(x_dimensions);
   check_dimensionality(dimensionality);
 
-  check_axis(axis, dimensionality, rray_args.axis, error_call);
+  r_obj* titles = KEEP(rray_titles(x, arg, error_call));
+
+  const int c_axis =
+    arg_as_axis(axis, titles, dimensionality, rray_args.axis, arg, error_call);
 
   const rray_locate_fn fn = rray_locate_switch(x, op, arg, error_call);
 
   r_obj* out_dimensions = KEEP(r_alloc_integer(dimensionality));
   int* v_out_dimensions = r_int_begin(out_dimensions);
   r_memcpy(v_out_dimensions, v_x_dimensions, sizeof(int) * dimensionality);
-  v_out_dimensions[axis - 1] = 1;
+  v_out_dimensions[c_axis - 1] = 1;
 
-  r_obj* out =
-    KEEP(fn(x, na_rm, v_x_dimensions, v_out_dimensions, dimensionality, axis));
+  r_obj* out = KEEP(
+    fn(x, na_rm, v_x_dimensions, v_out_dimensions, dimensionality, c_axis)
+  );
 
   r_attrib_poke_dim(out, out_dimensions);
 
-  r_obj* axes = KEEP(r_int(axis));
+  r_obj* axes = KEEP(r_int(c_axis));
   r_obj* out_names = KEEP(rray_reduce_names(x, axes));
 
   if (out_names != r_null) {
     r_attrib_poke_dim_names(out, out_names);
   }
 
-  FREE(6);
+  FREE(7);
   return out;
 }
 
diff --git a/src/locate.h b/src/locate.h
index c6cbbccf..ea47abe4 100644
--- a/src/locate.h
+++ b/src/locate.h
@@ -7,7 +7,7 @@
 
 r_obj* rray_locate_max(
   r_obj* x,
-  int axis,
+  r_obj* axis,
   bool na_rm,
   struct rray_arg* arg,
   struct r_lazy error_call
@@ -15,7 +15,7 @@ r_obj* rray_locate_max(
 
 r_obj* rray_locate_min(
   r_obj* x,
-  int axis,
+  r_obj* axis,
   bool na_rm,
   struct rray_arg* arg,
   struct r_lazy error_call
diff --git a/src/names.c b/src/names.c
index 452deda4..3e1f0865 100644
--- a/src/names.c
+++ b/src/names.c
@@ -3,6 +3,7 @@
 #include "axes.h"
 #include "dimensionality.h"
 #include "dimensions.h"
+#include "globals.h"
 #include "utils.h"
 #include "view.h"
 
@@ -23,23 +24,22 @@ r_obj* rray_names(r_obj* x, struct rray_arg* arg, struct r_lazy error_call) {
 
 r_obj* ffi_rray_axis_names(r_obj* ffi_x, r_obj* ffi_axis, r_obj* ffi_frame) {
   struct r_lazy error_call = {.x = ffi_frame, .env = r_null};
-  const int axis = arg_as_int(ffi_axis, rray_args.axis, error_call);
-  return rray_axis_names(ffi_x, axis, rray_args.x, error_call);
+  return rray_axis_names(ffi_x, ffi_axis, rray_args.x, error_call);
 }
 
 r_obj* ffi_rray_row_names(r_obj* ffi_x, r_obj* ffi_frame) {
   struct r_lazy error_call = {.x = ffi_frame, .env = r_null};
-  return rray_axis_names(ffi_x, 1, rray_args.x, error_call);
+  return rray_axis_names(ffi_x, rray_globals.one_int, rray_args.x, error_call);
 }
 
 r_obj* ffi_rray_column_names(r_obj* ffi_x, r_obj* ffi_frame) {
   struct r_lazy error_call = {.x = ffi_frame, .env = r_null};
-  return rray_axis_names(ffi_x, 2, rray_args.x, error_call);
+  return rray_axis_names(ffi_x, rray_globals.two_int, rray_args.x, error_call);
 }
 
 r_obj* rray_axis_names(
   r_obj* x,
-  int axis,
+  r_obj* axis,
   struct rray_arg* arg,
   struct r_lazy error_call
 ) {
@@ -47,11 +47,14 @@ r_obj* rray_axis_names(
   x = KEEP(arg_as_array(x, arg, error_call));
 
   const int dimensionality = rray_dimensionality(x, arg, error_call);
-  check_axis(axis, dimensionality, rray_args.axis, error_call);
 
   r_obj* names = rray_names(x, arg, error_call);
+  r_obj* titles = (names == r_null) ? r_null : r_names(names);
+
+  const int c_axis =
+    arg_as_axis(axis, titles, dimensionality, rray_args.axis, arg, error_call);
 
-  r_obj* out = (names == r_null) ? r_null : r_list_get(names, axis - 1);
+  r_obj* out = (names == r_null) ? r_null : r_list_get(names, c_axis - 1);
 
   FREE(1);
   return out;
@@ -120,8 +123,13 @@ r_obj* ffi_rray_set_axis_names(
   r_obj* ffi_frame
 ) {
   struct r_lazy error_call = {.x = ffi_frame, .env = r_null};
-  const int axis = arg_as_int(ffi_axis, rray_args.axis, error_call);
-  return rray_set_axis_names(ffi_x, axis, ffi_names, rray_args.x, error_call);
+  return rray_set_axis_names(
+    ffi_x,
+    ffi_axis,
+    ffi_names,
+    rray_args.x,
+    error_call
+  );
 }
 
 r_obj* ffi_rray_set_row_names(
@@ -130,7 +138,13 @@ r_obj* ffi_rray_set_row_names(
   r_obj* ffi_frame
 ) {
   struct r_lazy error_call = {.x = ffi_frame, .env = r_null};
-  return rray_set_axis_names(ffi_x, 1, ffi_names, rray_args.x, error_call);
+  return rray_set_axis_names(
+    ffi_x,
+    rray_globals.one_int,
+    ffi_names,
+    rray_args.x,
+    error_call
+  );
 }
 
 r_obj* ffi_rray_set_column_names(
@@ -139,12 +153,18 @@ r_obj* ffi_rray_set_column_names(
   r_obj* ffi_frame
 ) {
   struct r_lazy error_call = {.x = ffi_frame, .env = r_null};
-  return rray_set_axis_names(ffi_x, 2, ffi_names, rray_args.x, error_call);
+  return rray_set_axis_names(
+    ffi_x,
+    rray_globals.two_int,
+    ffi_names,
+    rray_args.x,
+    error_call
+  );
 }
 
 r_obj* rray_set_axis_names(
   r_obj* x,
-  int axis,
+  r_obj* axis,
   r_obj* names,
   struct rray_arg* arg,
   struct r_lazy error_call
@@ -153,17 +173,20 @@ r_obj* rray_set_axis_names(
   x = KEEP(arg_as_array(x, arg, error_call));
 
   const int dimensionality = rray_dimensionality(x, arg, error_call);
-  check_axis(axis, dimensionality, rray_args.axis, error_call);
-
-  const int dimension = rray_dimension(x, axis, arg, error_call);
-  check_axis_names(names, axis, dimension, error_call);
 
   r_obj* old_names = r_dim_names(x);
+  r_obj* titles = (old_names == r_null) ? r_null : r_names(old_names);
+
+  const int c_axis =
+    arg_as_axis(axis, titles, dimensionality, rray_args.axis, arg, error_call);
+
+  const int dimension = rray_dimension(x, c_axis, arg, error_call);
+  check_axis_names(names, c_axis, dimension, error_call);
 
   r_obj* new_names = KEEP(
     old_names == r_null ? r_alloc_list(dimensionality) : r_clone(old_names)
   );
-  r_list_poke(new_names, axis - 1, names);
+  r_list_poke(new_names, c_axis - 1, names);
 
   r_obj* out = KEEP(r_view(x));
   r_attrib_poke_dim(out, r_dim(x));
diff --git a/src/names.h b/src/names.h
index bf80a112..d34b3e89 100644
--- a/src/names.h
+++ b/src/names.h
@@ -9,7 +9,7 @@ r_obj* rray_names(r_obj* x, struct rray_arg* arg, struct r_lazy error_call);
 
 r_obj* rray_axis_names(
   r_obj* x,
-  int axis,
+  r_obj* axis,
   struct rray_arg* arg,
   struct r_lazy error_call
 );
@@ -23,7 +23,7 @@ r_obj* rray_set_names(
 
 r_obj* rray_set_axis_names(
   r_obj* x,
-  int axis,
+  r_obj* axis,
   r_obj* names,
   struct rray_arg* arg,
   struct r_lazy error_call
diff --git a/src/rep-each.c b/src/rep-each.c
index dcc1619a..9c655469 100644
--- a/src/rep-each.c
+++ b/src/rep-each.c
@@ -6,6 +6,7 @@
 #include "dimensionality.h"
 #include "rep.h"
 #include "slice.h"
+#include "titles.h"
 #include "utils.h"
 
 #include "decl/rep-each-decl.h"
@@ -17,14 +18,13 @@ r_obj* ffi_rray_rep_each(
   r_obj* ffi_frame
 ) {
   struct r_lazy error_call = {.x = ffi_frame, .env = r_null};
-  const int axis = arg_as_int(ffi_axis, rray_args.axis, error_call);
-  return rray_rep_each(ffi_x, ffi_times, axis, rray_args.x, error_call);
+  return rray_rep_each(ffi_x, ffi_times, ffi_axis, rray_args.x, error_call);
 }
 
 r_obj* rray_rep_each(
   r_obj* x,
   r_obj* times,
-  int axis,
+  r_obj* axis,
   struct rray_arg* x_arg,
   struct r_lazy error_call
 ) {
@@ -36,8 +36,17 @@ r_obj* rray_rep_each(
   const int dimensionality = rray_dimensionality_from_dimensions(x_dimensions);
   check_dimensionality(dimensionality);
 
-  check_axis(axis, dimensionality, rray_args.axis, error_call);
-  const int axis_dimension = v_x_dimensions[axis - 1];
+  r_obj* titles = KEEP(rray_titles(x, x_arg, error_call));
+
+  const int c_axis = arg_as_axis(
+    axis,
+    titles,
+    dimensionality,
+    rray_args.axis,
+    x_arg,
+    error_call
+  );
+  const int axis_dimension = v_x_dimensions[c_axis - 1];
 
   times = KEEP(
     arg_as_rep_each_times(times, axis_dimension, rray_args.times, error_call)
@@ -56,13 +65,13 @@ r_obj* rray_rep_each(
 
   r_list_poke(
     indices,
-    axis - 1,
+    c_axis - 1,
     rray_rep_each_locations(axis_dimension, out_dimension, v_times, times_size)
   );
 
   r_obj* out = rray_slice(x, indices, x_arg, rray_args.empty, error_call);
 
-  FREE(3);
+  FREE(4);
   return out;
 }
 
diff --git a/src/rep-each.h b/src/rep-each.h
index 5fd3e2f2..a96e322a 100644
--- a/src/rep-each.h
+++ b/src/rep-each.h
@@ -8,7 +8,7 @@
 r_obj* rray_rep_each(
   r_obj* x,
   r_obj* times,
-  int axis,
+  r_obj* axis,
   struct rray_arg* x_arg,
   struct r_lazy error_call
 );
diff --git a/src/roll-each.c b/src/roll-each.c
index c460b3a0..dd86b6f6 100644
--- a/src/roll-each.c
+++ b/src/roll-each.c
@@ -7,6 +7,7 @@
 #include "reduce-names.h"
 #include "roll.h"
 #include "size.h"
+#include "titles.h"
 #include "utils.h"
 
 #include "decl/roll-each-decl.h"
@@ -18,14 +19,13 @@ r_obj* ffi_rray_roll_each(
   r_obj* ffi_frame
 ) {
   struct r_lazy error_call = {.x = ffi_frame, .env = r_null};
-  const int axis = arg_as_int(ffi_axis, rray_args.axis, error_call);
-  return rray_roll_each(ffi_x, ffi_n, axis, rray_args.x, error_call);
+  return rray_roll_each(ffi_x, ffi_n, ffi_axis, rray_args.x, error_call);
 }
 
 r_obj* rray_roll_each(
   r_obj* x,
   r_obj* n,
-  int axis,
+  r_obj* axis,
   struct rray_arg* x_arg,
   struct r_lazy error_call
 ) {
@@ -37,15 +37,24 @@ r_obj* rray_roll_each(
   const int dimensionality = rray_dimensionality_from_dimensions(x_dimensions);
   check_dimensionality(dimensionality);
 
-  check_axis(axis, dimensionality, rray_args.axis, error_call);
-  const int axis_dimension = v_x_dimensions[axis - 1];
+  r_obj* titles = KEEP(rray_titles(x, x_arg, error_call));
+
+  const int c_axis = arg_as_axis(
+    axis,
+    titles,
+    dimensionality,
+    rray_args.axis,
+    x_arg,
+    error_call
+  );
+  const int axis_dimension = v_x_dimensions[c_axis - 1];
 
   n = KEEP(arg_as_roll_each_n(n, rray_args.n, error_call));
   n = KEEP(rray_roll_each_normalize(n, axis_dimension));
 
   r_obj* n_broadcast_dimensions = KEEP(r_clone(x_dimensions));
   int* v_n_broadcast_dimensions = r_int_begin(n_broadcast_dimensions);
-  v_n_broadcast_dimensions[axis - 1] = 1;
+  v_n_broadcast_dimensions[c_axis - 1] = 1;
 
   // Nicely simplifies the loop to explicitly broadcast `n`. Cost is fairly
   // cheap, since one dimension of `x` is set to 1.
@@ -59,12 +68,12 @@ r_obj* rray_roll_each(
   r_attrib_poke_dim(out, x_dimensions);
 
   r_ssize block_size = 1;
-  for (int i = 0; i < axis - 1; ++i) {
+  for (int i = 0; i < c_axis - 1; ++i) {
     block_size *= v_x_dimensions[i];
   }
 
   r_ssize n_groups = 1;
-  for (int i = axis; i < dimensionality; ++i) {
+  for (int i = c_axis; i < dimensionality; ++i) {
     n_groups *= v_x_dimensions[i];
   }
 
@@ -72,14 +81,14 @@ r_obj* rray_roll_each(
 
   // Using `rray_reduce_names()` is an easy way to clear the `axis` names, which
   // likely no longer make sense
-  r_obj* axes = KEEP(r_int(axis));
+  r_obj* axes = KEEP(r_int(c_axis));
   r_obj* out_names = KEEP(rray_reduce_names(x, axes));
 
   if (out_names != r_null) {
     r_attrib_poke_dim_names(out, out_names);
   }
 
-  FREE(8);
+  FREE(9);
   return out;
 }
 
diff --git a/src/roll-each.h b/src/roll-each.h
index c214d8ae..7c0484f0 100644
--- a/src/roll-each.h
+++ b/src/roll-each.h
@@ -8,7 +8,7 @@
 r_obj* rray_roll_each(
   r_obj* x,
   r_obj* n,
-  int axis,
+  r_obj* axis,
   struct rray_arg* x_arg,
   struct r_lazy error_call
 );
diff --git a/src/slice-axis.c b/src/slice-axis.c
index c1c3a606..29bacb8f 100644
--- a/src/slice-axis.c
+++ b/src/slice-axis.c
@@ -2,8 +2,10 @@
 
 #include "axes.h"
 #include "dimensionality.h"
+#include "globals.h"
 #include "slice-assign.h"
 #include "slice.h"
+#include "titles.h"
 #include "utils.h"
 
 #include "decl/slice-axis-decl.h"
@@ -15,11 +17,10 @@ r_obj* ffi_rray_slice_axis(
   r_obj* ffi_frame
 ) {
   struct r_lazy error_call = {.x = ffi_frame, .env = r_null};
-  const int axis = arg_as_int(ffi_axis, rray_args.axis, error_call);
   return rray_slice_axis(
     ffi_x,
     ffi_i,
-    axis,
+    ffi_axis,
     rray_args.x,
     rray_args.i,
     error_call
@@ -28,18 +29,32 @@ r_obj* ffi_rray_slice_axis(
 
 r_obj* ffi_rray_slice_rows(r_obj* ffi_x, r_obj* ffi_i, r_obj* ffi_frame) {
   struct r_lazy error_call = {.x = ffi_frame, .env = r_null};
-  return rray_slice_axis(ffi_x, ffi_i, 1, rray_args.x, rray_args.i, error_call);
+  return rray_slice_axis(
+    ffi_x,
+    ffi_i,
+    rray_globals.one_int,
+    rray_args.x,
+    rray_args.i,
+    error_call
+  );
 }
 
 r_obj* ffi_rray_slice_columns(r_obj* ffi_x, r_obj* ffi_i, r_obj* ffi_frame) {
   struct r_lazy error_call = {.x = ffi_frame, .env = r_null};
-  return rray_slice_axis(ffi_x, ffi_i, 2, rray_args.x, rray_args.i, error_call);
+  return rray_slice_axis(
+    ffi_x,
+    ffi_i,
+    rray_globals.two_int,
+    rray_args.x,
+    rray_args.i,
+    error_call
+  );
 }
 
 r_obj* rray_slice_axis(
   r_obj* x,
   r_obj* i,
-  int axis,
+  r_obj* axis,
   struct rray_arg* x_arg,
   struct rray_arg* i_arg,
   struct r_lazy error_call
@@ -48,14 +63,24 @@ r_obj* rray_slice_axis(
   x = KEEP(arg_as_array(x, x_arg, error_call));
 
   const int dimensionality = rray_dimensionality(x, x_arg, error_call);
-  check_axis(axis, dimensionality, rray_args.axis, error_call);
+
+  r_obj* titles = KEEP(rray_titles(x, x_arg, error_call));
+
+  const int c_axis = arg_as_axis(
+    axis,
+    titles,
+    dimensionality,
+    rray_args.axis,
+    x_arg,
+    error_call
+  );
 
   r_obj* indices =
-    KEEP(rray_slice_axis_indices(i, axis, dimensionality, i_arg));
+    KEEP(rray_slice_axis_indices(i, c_axis, dimensionality, i_arg));
 
   r_obj* out = rray_slice(x, indices, x_arg, rray_args.empty, error_call);
 
-  FREE(2);
+  FREE(3);
   return out;
 }
 
@@ -67,11 +92,10 @@ r_obj* ffi_rray_slice_assign_axis(
   r_obj* ffi_frame
 ) {
   struct r_lazy error_call = {.x = ffi_frame, .env = r_null};
-  const int axis = arg_as_int(ffi_axis, rray_args.axis, error_call);
   return rray_slice_assign_axis(
     ffi_x,
     ffi_i,
-    axis,
+    ffi_axis,
     ffi_value,
     rray_args.x,
     rray_args.i,
@@ -90,7 +114,7 @@ r_obj* ffi_rray_slice_assign_rows(
   return rray_slice_assign_axis(
     ffi_x,
     ffi_i,
-    1,
+    rray_globals.one_int,
     ffi_value,
     rray_args.x,
     rray_args.i,
@@ -109,7 +133,7 @@ r_obj* ffi_rray_slice_assign_columns(
   return rray_slice_assign_axis(
     ffi_x,
     ffi_i,
-    2,
+    rray_globals.two_int,
     ffi_value,
     rray_args.x,
     rray_args.i,
@@ -121,7 +145,7 @@ r_obj* ffi_rray_slice_assign_columns(
 r_obj* rray_slice_assign_axis(
   r_obj* x,
   r_obj* i,
-  int axis,
+  r_obj* axis,
   r_obj* value,
   struct rray_arg* x_arg,
   struct rray_arg* i_arg,
@@ -132,10 +156,20 @@ r_obj* rray_slice_assign_axis(
   x = KEEP(arg_as_array(x, x_arg, error_call));
 
   const int dimensionality = rray_dimensionality(x, x_arg, error_call);
-  check_axis(axis, dimensionality, rray_args.axis, error_call);
+
+  r_obj* titles = KEEP(rray_titles(x, x_arg, error_call));
+
+  const int c_axis = arg_as_axis(
+    axis,
+    titles,
+    dimensionality,
+    rray_args.axis,
+    x_arg,
+    error_call
+  );
 
   r_obj* indices =
-    KEEP(rray_slice_axis_indices(i, axis, dimensionality, i_arg));
+    KEEP(rray_slice_axis_indices(i, c_axis, dimensionality, i_arg));
 
   r_obj* out = rray_slice_assign(
     x,
@@ -147,7 +181,7 @@ r_obj* rray_slice_assign_axis(
     error_call
   );
 
-  FREE(2);
+  FREE(3);
   return out;
 }
 
diff --git a/src/slice-axis.h b/src/slice-axis.h
index 5f9413f6..3b6c47c3 100644
--- a/src/slice-axis.h
+++ b/src/slice-axis.h
@@ -8,7 +8,7 @@
 r_obj* rray_slice_axis(
   r_obj* x,
   r_obj* i,
-  int axis,
+  r_obj* axis,
   struct rray_arg* x_arg,
   struct rray_arg* i_arg,
   struct r_lazy error_call
@@ -17,7 +17,7 @@ r_obj* rray_slice_axis(
 r_obj* rray_slice_assign_axis(
   r_obj* x,
   r_obj* i,
-  int axis,
+  r_obj* axis,
   r_obj* value,
   struct rray_arg* x_arg,
   struct rray_arg* i_arg,
diff --git a/src/split.c b/src/split.c
index 2d096c84..8431001f 100644
--- a/src/split.c
+++ b/src/split.c
@@ -16,13 +16,12 @@ r_obj* ffi_rray_split(
   r_obj* ffi_frame
 ) {
   struct r_lazy error_call = {.x = ffi_frame, .env = r_null};
-  const int axis = arg_as_int(ffi_axis, rray_args.axis, error_call);
-  return rray_split(ffi_x, axis, ffi_dimensions, rray_args.x, error_call);
+  return rray_split(ffi_x, ffi_axis, ffi_dimensions, rray_args.x, error_call);
 }
 
 r_obj* rray_split(
   r_obj* x,
-  int axis,
+  r_obj* axis,
   r_obj* dimensions,
   struct rray_arg* arg,
   struct r_lazy error_call
@@ -35,8 +34,19 @@ r_obj* rray_split(
   const int dimensionality = rray_dimensionality_from_dimensions(x_dimensions);
   check_dimensionality(dimensionality);
 
-  check_axis(axis, dimensionality, rray_args.axis, error_call);
-  const int axis_dimension = v_x_dimensions[axis - 1];
+  r_obj* x_names = r_dim_names(x);
+  r_obj* const* v_x_names = (x_names == r_null) ? NULL : r_list_cbegin(x_names);
+  r_obj* x_titles = (x_names == r_null) ? r_null : r_names(x_names);
+
+  const int c_axis = arg_as_axis(
+    axis,
+    x_titles,
+    dimensionality,
+    rray_args.axis,
+    arg,
+    error_call
+  );
+  const int axis_dimension = v_x_dimensions[c_axis - 1];
 
   dimensions = KEEP(arg_as_non_negative_bare_integer(
     dimensions,
@@ -59,11 +69,7 @@ r_obj* rray_split(
 
   r_obj* out = KEEP(r_alloc_list(out_size));
 
-  r_obj* x_names = r_dim_names(x);
-  r_obj* const* v_x_names = (x_names == r_null) ? NULL : r_list_cbegin(x_names);
-  r_obj* x_titles = (x_names == r_null) ? r_null : r_names(x_names);
-
-  r_obj* x_axis_names = (v_x_names == NULL) ? r_null : v_x_names[axis - 1];
+  r_obj* x_axis_names = (v_x_names == NULL) ? r_null : v_x_names[c_axis - 1];
   r_obj* const* v_x_axis_names =
     (x_axis_names == r_null) ? NULL : r_chr_cbegin(x_axis_names);
 
@@ -73,7 +79,7 @@ r_obj* rray_split(
     dimensionality,
     v_x_strides
   );
-  const r_ssize x_axis_stride = v_x_strides[axis - 1];
+  const r_ssize x_axis_stride = v_x_strides[c_axis - 1];
 
   const enum r_type type = r_typeof(x);
 
@@ -109,7 +115,7 @@ r_obj* rray_split(
         v_x_dimensions,
         sizeof(int) * dimensionality
       );
-      v_out_elt_dimensions[axis - 1] = dimension;
+      v_out_elt_dimensions[c_axis - 1] = dimension;
 
       rray_run_iterator_init1(
         &it,
@@ -131,7 +137,7 @@ r_obj* rray_split(
         v_x_names,
         x_titles,
         dimensionality,
-        axis,
+        c_axis,
         v_x_axis_names,
         x_axis_start,
         dimension
diff --git a/src/split.h b/src/split.h
index 9fef3120..567d9f48 100644
--- a/src/split.h
+++ b/src/split.h
@@ -7,7 +7,7 @@
 
 r_obj* rray_split(
   r_obj* x,
-  int axis,
+  r_obj* axis,
   r_obj* dimensions,
   struct rray_arg* arg,
   struct r_lazy error_call
diff --git a/src/stack.c b/src/stack.c
index c2946a88..d9ec6ecd 100644
--- a/src/stack.c
+++ b/src/stack.c
@@ -57,7 +57,9 @@ r_obj* rray_stack(
 
   r_obj* names = KEEP(r_names(xs));
   if (names != r_null) {
-    out = rray_set_axis_names(out, axis, names, arg, error_call);
+    r_obj* axis_obj = KEEP(r_int(axis));
+    out = rray_set_axis_names(out, axis_obj, names, arg, error_call);
+    FREE(1);
   }
 
   FREE(4);
diff --git a/src/titles.c b/src/titles.c
index dfffc0b9..80a5bd1d 100644
--- a/src/titles.c
+++ b/src/titles.c
@@ -113,13 +113,18 @@ r_obj* ffi_rray_set_axis_title(
   r_obj* ffi_frame
 ) {
   struct r_lazy error_call = {.x = ffi_frame, .env = r_null};
-  const int axis = arg_as_int(ffi_axis, rray_args.axis, error_call);
-  return rray_set_axis_title(ffi_x, axis, ffi_title, rray_args.x, error_call);
+  return rray_set_axis_title(
+    ffi_x,
+    ffi_axis,
+    ffi_title,
+    rray_args.x,
+    error_call
+  );
 }
 
 r_obj* rray_set_axis_title(
   r_obj* x,
-  int axis,
+  r_obj* axis,
   r_obj* title,
   struct rray_arg* arg,
   struct r_lazy error_call
@@ -128,10 +133,21 @@ r_obj* rray_set_axis_title(
   x = KEEP(arg_as_array(x, arg, error_call));
 
   const int dimensionality = rray_dimensionality(x, arg, error_call);
-  check_axis(axis, dimensionality, rray_args.axis, error_call);
+
+  r_obj* names = r_dim_names(x);
+  r_obj* old_titles = names == r_null ? r_null : r_names(names);
+
+  const int c_axis = arg_as_axis(
+    axis,
+    old_titles,
+    dimensionality,
+    rray_args.axis,
+    arg,
+    error_call
+  );
 
   if (title == r_null) {
-    r_obj* out = rray_clear_axis_title(x, axis, arg, error_call);
+    r_obj* out = rray_clear_axis_title(x, c_axis, arg, error_call);
     FREE(1);
     return out;
   }
@@ -154,9 +170,6 @@ r_obj* rray_set_axis_title(
     );
   }
 
-  r_obj* names = r_dim_names(x);
-  r_obj* old_titles = names == r_null ? r_null : r_names(names);
-
   r_obj* new_titles = KEEP(r_alloc_character(dimensionality));
 
   if (old_titles != r_null) {
@@ -166,7 +179,7 @@ r_obj* rray_set_axis_title(
     }
   }
 
-  r_chr_poke(new_titles, axis - 1, r_chr_get(title, 0));
+  r_chr_poke(new_titles, c_axis - 1, r_chr_get(title, 0));
 
   r_obj* out = KEEP(rray_set_titles(x, new_titles, arg, error_call));
 
diff --git a/src/titles.h b/src/titles.h
index 372f5430..50fd76f9 100644
--- a/src/titles.h
+++ b/src/titles.h
@@ -23,7 +23,7 @@ r_obj* rray_set_titles(
 
 r_obj* rray_set_axis_title(
   r_obj* x,
-  int axis,
+  r_obj* axis,
   r_obj* title,
   struct rray_arg* arg,
   struct r_lazy error_call
diff --git a/src/unstack.c b/src/unstack.c
index 66b5eca9..0bdc4278 100644
--- a/src/unstack.c
+++ b/src/unstack.c
@@ -2,20 +2,21 @@
 
 #include "axes.h"
 #include "dimensionality.h"
+#include "globals.h"
 #include "names.h"
 #include "remove-axes.h"
 #include "split.h"
+#include "titles.h"
 #include "utils.h"
 
 r_obj* ffi_rray_unstack(r_obj* ffi_x, r_obj* ffi_axis, r_obj* ffi_frame) {
   struct r_lazy error_call = {.x = ffi_frame, .env = r_null};
-  const int axis = arg_as_int(ffi_axis, rray_args.axis, error_call);
-  return rray_unstack(ffi_x, axis, rray_args.x, error_call);
+  return rray_unstack(ffi_x, ffi_axis, rray_args.x, error_call);
 }
 
 r_obj* rray_unstack(
   r_obj* x,
-  int axis,
+  r_obj* axis,
   struct rray_arg* arg,
   struct r_lazy error_call
 ) {
@@ -34,12 +35,15 @@ r_obj* rray_unstack(
     );
   }
 
-  check_axis(axis, dimensionality, rray_args.axis, error_call);
+  r_obj* titles = KEEP(rray_titles(x, arg, error_call));
 
-  r_obj* dimensions = KEEP(r_int(1));
-  r_obj* out = KEEP(rray_split(x, axis, dimensions, arg, error_call));
+  const int c_axis =
+    arg_as_axis(axis, titles, dimensionality, rray_args.axis, arg, error_call);
+
+  r_obj* axes = KEEP(r_int(c_axis));
+
+  r_obj* out = KEEP(rray_split(x, axes, rray_globals.one_int, arg, error_call));
 
-  r_obj* axes = KEEP(r_int(axis));
   const r_ssize out_size = r_length(out);
 
   for (r_ssize i = 0; i < out_size; ++i) {
@@ -47,7 +51,7 @@ r_obj* rray_unstack(
     r_list_poke(out, i, rray_remove_axes(elt, axes, arg, error_call));
   }
 
-  r_obj* names = KEEP(rray_axis_names(x, axis, arg, error_call));
+  r_obj* names = KEEP(rray_axis_names(x, axes, arg, error_call));
   if (names != r_null) {
     r_attrib_poke_names(out, names);
   }
diff --git a/src/unstack.h b/src/unstack.h
index 21f35d95..f6df26be 100644
--- a/src/unstack.h
+++ b/src/unstack.h
@@ -7,7 +7,7 @@
 
 r_obj* rray_unstack(
   r_obj* x,
-  int axis,
+  r_obj* axis,
   struct rray_arg* arg,
   struct r_lazy error_call
 );
diff --git a/tests/testthat/_snaps/locate.md b/tests/testthat/_snaps/locate.md
index 7f24ea28..d375c653 100644
--- a/tests/testthat/_snaps/locate.md
+++ b/tests/testthat/_snaps/locate.md
@@ -20,7 +20,7 @@
       rray_locate_max(x, axis = c(1L, 2L))
     Condition
       Error in `rray_locate_max()`:
-      ! `axis` must be a single integer, not length 2.
+      ! `axis` must be length 1, not length 2.
 
 ---
 
@@ -38,6 +38,22 @@
       Error in `rray_locate_min()`:
       ! `axis` must contain whole numbers that fit in an integer. Problem at location 1.
 
+---
+
+    Code
+      rray_locate_min(x, axis = "row")
+    Condition
+      Error in `rray_locate_min()`:
+      ! Can't use a title in `axis` because `x` has no titles.
+
+# errors on an unknown `axis` title
+
+    Code
+      rray_locate_max(x, axis = "nope")
+    Condition
+      Error in `rray_locate_max()`:
+      ! Can't find an axis of `x` titled "nope".
+
 # `axis` must be named
 
     Code
diff --git a/tests/testthat/_snaps/names.md b/tests/testthat/_snaps/names.md
index 8e126cbc..f9958bf6 100644
--- a/tests/testthat/_snaps/names.md
+++ b/tests/testthat/_snaps/names.md
@@ -52,7 +52,7 @@
       rray_axis_names(x, c(1, 2))
     Condition
       Error in `rray_axis_names()`:
-      ! `axis` must be a single integer, not length 2.
+      ! `axis` must be length 1, not length 2.
 
 ---
 
@@ -60,7 +60,23 @@
       rray_axis_names(x, integer())
     Condition
       Error in `rray_axis_names()`:
-      ! `axis` must be a single integer, not length 0.
+      ! `axis` must be length 1, not length 0.
+
+---
+
+    Code
+      rray_axis_names(x, "row")
+    Condition
+      Error in `rray_axis_names()`:
+      ! Can't use a title in `axis` because `x` has no titles.
+
+# rray_axis_names() errors on an unknown title
+
+    Code
+      rray_axis_names(x, "nope")
+    Condition
+      Error in `rray_axis_names()`:
+      ! Can't find an axis of `x` titled "nope".
 
 # rray_axis_names() errors on classed input
 
@@ -158,6 +174,22 @@
       Error in `rray_set_axis_names()`:
       ! `axis` must be less than or equal to the dimensionality of 2, not 3.
 
+---
+
+    Code
+      rray_set_axis_names(x, "row", "a")
+    Condition
+      Error in `rray_set_axis_names()`:
+      ! Can't use a title in `axis` because `x` has no titles.
+
+# rray_set_axis_names() errors on an unknown title
+
+    Code
+      rray_set_axis_names(x, "nope", "a")
+    Condition
+      Error in `rray_set_axis_names()`:
+      ! Can't find an axis of `x` titled "nope".
+
 # rray_set_axis_names() errors if names aren't character or NULL
 
     Code
diff --git a/tests/testthat/_snaps/rep.md b/tests/testthat/_snaps/rep.md
index 665e82ce..7444892d 100644
--- a/tests/testthat/_snaps/rep.md
+++ b/tests/testthat/_snaps/rep.md
@@ -301,3 +301,11 @@
       Error in `rray_rep_each()`:
       ! `axis` must be less than or equal to the dimensionality of 2, not 3.
 
+---
+
+    Code
+      rray_rep_each(x, times = 2, axis = "row")
+    Condition
+      Error in `rray_rep_each()`:
+      ! Can't use a title in `axis` because `x` has no titles.
+
diff --git a/tests/testthat/_snaps/roll.md b/tests/testthat/_snaps/roll.md
index 15bdca30..999599b2 100644
--- a/tests/testthat/_snaps/roll.md
+++ b/tests/testthat/_snaps/roll.md
@@ -180,7 +180,7 @@
       rray_roll_each(x, n = 1, axis = c(1, 2))
     Condition
       Error in `rray_roll_each()`:
-      ! `axis` must be a single integer, not length 2.
+      ! `axis` must be length 1, not length 2.
 
 ---
 
@@ -206,6 +206,14 @@
       Error in `rray_roll_each()`:
       ! `axis` must not be missing.
 
+---
+
+    Code
+      rray_roll_each(x, n = 1, axis = "row")
+    Condition
+      Error in `rray_roll_each()`:
+      ! Can't use a title in `axis` because `x` has no titles.
+
 # `n` must broadcast to `x` with `axis` set to 1
 
     Code
diff --git a/tests/testthat/_snaps/slice.md b/tests/testthat/_snaps/slice.md
index c2d2dbf8..da2ac1b8 100644
--- a/tests/testthat/_snaps/slice.md
+++ b/tests/testthat/_snaps/slice.md
@@ -124,12 +124,17 @@
       rray_slice_axis(x, 1L, axis = c(1, 2))
     Condition
       Error in `rray_slice_axis()`:
-      ! `axis` must be a single integer, not length 2.
+      ! `axis` must be length 1, not length 2.
     Code
       rray_slice_axis(x, 1L, axis = NA_integer_)
     Condition
       Error in `rray_slice_axis()`:
       ! `axis` must not be missing.
+    Code
+      rray_slice_axis(x, 1L, axis = "row")
+    Condition
+      Error in `rray_slice_axis()`:
+      ! Can't use a title in `axis` because `x` has no titles.
 
 # errors on unsupported `x` inputs to `rray_slice_axis()`
 
@@ -275,6 +280,11 @@
     Condition
       Error in `rray_slice_assign_axis()`:
       ! `axis` must be less than or equal to the dimensionality of 2, not 3.
+    Code
+      rray_slice_assign_axis(x, 1L, axis = "row", value = 0L)
+    Condition
+      Error in `rray_slice_assign_axis()`:
+      ! Can't use a title in `axis` because `x` has no titles.
     Code
       rray_slice_assign_axis(x, 1L, axis = 1, value = "a")
     Condition
diff --git a/tests/testthat/_snaps/split.md b/tests/testthat/_snaps/split.md
index 6406c54e..383271a7 100644
--- a/tests/testthat/_snaps/split.md
+++ b/tests/testthat/_snaps/split.md
@@ -40,7 +40,7 @@
       rray_split(x, axis = c(1, 2), dimensions = 1)
     Condition
       Error in `rray_split()`:
-      ! `axis` must be a single integer, not length 2.
+      ! `axis` must be length 1, not length 2.
 
 ---
 
@@ -58,6 +58,14 @@
       Error in `rray_split()`:
       ! `axis` must contain whole numbers that fit in an integer. Problem at location 1.
 
+---
+
+    Code
+      rray_split(x, axis = "row", dimensions = 1)
+    Condition
+      Error in `rray_split()`:
+      ! Can't use a title in `axis` because `x` has no titles.
+
 ---
 
     Code
diff --git a/tests/testthat/_snaps/titles.md b/tests/testthat/_snaps/titles.md
index 9453e083..839d19a3 100644
--- a/tests/testthat/_snaps/titles.md
+++ b/tests/testthat/_snaps/titles.md
@@ -46,6 +46,14 @@
       Error in `rray_axis_title()`:
       ! `axis` must be a single integer, not length 2.
 
+---
+
+    Code
+      rray_axis_title(x, "Row")
+    Condition
+      Error in `rray_axis_title()`:
+      ! `axis` must be an integer or double vector, not the string "Row".
+
 # title setters reject invalid input and values
 
     Code
@@ -78,6 +86,14 @@
       Error in `rray_set_axis_title()`:
       ! `axis` must be greater than or equal to 1, not 0.
 
+---
+
+    Code
+      rray_set_axis_title(x, "Row", "R")
+    Condition
+      Error in `rray_set_axis_title()`:
+      ! Can't use a title in `axis` because `x` has no titles.
+
 ---
 
     Code
diff --git a/tests/testthat/_snaps/unstack.md b/tests/testthat/_snaps/unstack.md
index 12d8502e..86efaec4 100644
--- a/tests/testthat/_snaps/unstack.md
+++ b/tests/testthat/_snaps/unstack.md
@@ -20,7 +20,7 @@
       rray_unstack(x, axis = c(1, 2))
     Condition
       Error in `rray_unstack()`:
-      ! `axis` must be a single integer, not length 2.
+      ! `axis` must be length 1, not length 2.
 
 ---
 
@@ -38,6 +38,14 @@
       Error in `rray_unstack()`:
       ! `axis` must contain whole numbers that fit in an integer. Problem at location 1.
 
+---
+
+    Code
+      rray_unstack(x, axis = "row")
+    Condition
+      Error in `rray_unstack()`:
+      ! Can't use a title in `axis` because `x` has no titles.
+
 ---
 
     Code
diff --git a/tests/testthat/test-locate.R b/tests/testthat/test-locate.R
index bbf9896c..d21a8fb5 100644
--- a/tests/testthat/test-locate.R
+++ b/tests/testthat/test-locate.R
@@ -243,6 +243,18 @@ test_that("`axis` is coerced to integer", {
   expect_identical(rray_locate_min(x, axis = 1), rray_locate_min(x, axis = 1L))
 })
 
+test_that("`axis` can be a title", {
+  x <- array(1:6, c(2L, 3L), dimnames = list(row = NULL, col = NULL))
+  expect_identical(
+    rray_locate_max(x, axis = "col"),
+    rray_locate_max(x, axis = 2L)
+  )
+  expect_identical(
+    rray_locate_min(x, axis = "col"),
+    rray_locate_min(x, axis = 2L)
+  )
+})
+
 test_that("`axis` is validated", {
   x <- array(1:4, c(2L, 2L))
   expect_snapshot(rray_locate_max(x, axis = 0L), error = TRUE)
@@ -250,6 +262,12 @@ test_that("`axis` is validated", {
   expect_snapshot(rray_locate_max(x, axis = c(1L, 2L)), error = TRUE)
   expect_snapshot(rray_locate_max(x, axis = NA_integer_), error = TRUE)
   expect_snapshot(rray_locate_min(x, axis = 1.5), error = TRUE)
+  expect_snapshot(rray_locate_min(x, axis = "row"), error = TRUE)
+})
+
+test_that("errors on an unknown `axis` title", {
+  x <- array(1:6, c(2L, 3L), dimnames = list(row = NULL, col = NULL))
+  expect_snapshot(rray_locate_max(x, axis = "nope"), error = TRUE)
 })
 
 test_that("`axis` must be named", {
diff --git a/tests/testthat/test-names.R b/tests/testthat/test-names.R
index ca054db4..a7d9c557 100644
--- a/tests/testthat/test-names.R
+++ b/tests/testthat/test-names.R
@@ -70,6 +70,16 @@ test_that("rray_axis_names() coerces axis to integer", {
   expect_identical(rray_axis_names(x, 1), rray_axis_names(x, 1L))
 })
 
+test_that("rray_axis_names() takes a title for axis", {
+  x <- array(
+    1:6,
+    c(2, 3),
+    dimnames = list(row = NULL, col = c("c1", "c2", "c3"))
+  )
+  expect_identical(rray_axis_names(x, "col"), c("c1", "c2", "c3"))
+  expect_null(rray_axis_names(x, "row"))
+})
+
 test_that("rray_axis_names() errors on an invalid axis", {
   x <- array(1:6, c(2, 3))
   expect_snapshot(rray_axis_names(x, 0), error = TRUE)
@@ -77,6 +87,12 @@ test_that("rray_axis_names() errors on an invalid axis", {
   expect_snapshot(rray_axis_names(x, NA_integer_), error = TRUE)
   expect_snapshot(rray_axis_names(x, c(1, 2)), error = TRUE)
   expect_snapshot(rray_axis_names(x, integer()), error = TRUE)
+  expect_snapshot(rray_axis_names(x, "row"), error = TRUE)
+})
+
+test_that("rray_axis_names() errors on an unknown title", {
+  x <- array(1:6, c(2, 3), dimnames = list(row = NULL, col = NULL))
+  expect_snapshot(rray_axis_names(x, "nope"), error = TRUE)
 })
 
 test_that("rray_axis_names() errors on classed input", {
@@ -280,10 +296,24 @@ test_that("rray_set_axis_names() coerces axis to integer", {
   )
 })
 
+test_that("rray_set_axis_names() takes a title for axis", {
+  x <- array(1:6, c(2, 3), dimnames = list(row = NULL, col = NULL))
+  expect_identical(
+    rray_set_axis_names(x, "col", c("c1", "c2", "c3")),
+    rray_set_axis_names(x, 2, c("c1", "c2", "c3"))
+  )
+})
+
 test_that("rray_set_axis_names() errors on an invalid axis", {
   x <- array(1:6, c(2, 3))
   expect_snapshot(rray_set_axis_names(x, 0, "a"), error = TRUE)
   expect_snapshot(rray_set_axis_names(x, 3, "a"), error = TRUE)
+  expect_snapshot(rray_set_axis_names(x, "row", "a"), error = TRUE)
+})
+
+test_that("rray_set_axis_names() errors on an unknown title", {
+  x <- array(1:6, c(2, 3), dimnames = list(row = NULL, col = NULL))
+  expect_snapshot(rray_set_axis_names(x, "nope", "a"), error = TRUE)
 })
 
 test_that("rray_set_axis_names() errors if names aren't character or NULL", {
diff --git a/tests/testthat/test-rep.R b/tests/testthat/test-rep.R
index 493edfe6..53ab0c2c 100644
--- a/tests/testthat/test-rep.R
+++ b/tests/testthat/test-rep.R
@@ -512,6 +512,14 @@ test_that("`times` can be a double", {
   )
 })
 
+test_that("`axis` can be a title", {
+  x <- array(1:6, c(3L, 2L), dimnames = list(row = NULL, col = NULL))
+  expect_identical(
+    rray_rep_each(x, times = c(1, 2, 3), axis = "row"),
+    rray_rep_each(x, times = c(1, 2, 3), axis = 1)
+  )
+})
+
 test_that("names on the repeated axis repeat, and can be duplicated", {
   x <- array(1:6, c(3, 2), dimnames = list(c("a", "b", "c"), c("x", "y")))
 
@@ -603,6 +611,7 @@ test_that("`axis` is validated", {
   x <- array(1:6, c(3, 2))
   expect_snapshot(rray_rep_each(x, times = 2, axis = 0), error = TRUE)
   expect_snapshot(rray_rep_each(x, times = 2, axis = 3), error = TRUE)
+  expect_snapshot(rray_rep_each(x, times = 2, axis = "row"), error = TRUE)
 })
 
 test_that("`times` is validated", {
diff --git a/tests/testthat/test-roll.R b/tests/testthat/test-roll.R
index 19858810..47010fc8 100644
--- a/tests/testthat/test-roll.R
+++ b/tests/testthat/test-roll.R
@@ -525,6 +525,14 @@ test_that("`n` can be integerish doubles or logicals", {
   )
 })
 
+test_that("`axis` can be a title", {
+  x <- matrix(1:12, nrow = 3, dimnames = list(row = NULL, col = NULL))
+  expect_identical(
+    rray_roll_each(x, n = c(0, 1, 2), axis = "col"),
+    rray_roll_each(x, n = c(0, 1, 2), axis = 2)
+  )
+})
+
 test_that("works with a zero dimension", {
   x <- array(integer(), c(2, 0))
   expect_identical(rray_roll_each(x, n = c(1, 2), axis = 2), x)
@@ -588,6 +596,7 @@ test_that("`axis` is validated", {
   expect_snapshot(rray_roll_each(x, n = 1, axis = 3), error = TRUE)
   expect_snapshot(rray_roll_each(x, n = 1, axis = 0), error = TRUE)
   expect_snapshot(rray_roll_each(x, n = 1, axis = NA_integer_), error = TRUE)
+  expect_snapshot(rray_roll_each(x, n = 1, axis = "row"), error = TRUE)
 })
 
 test_that("`n` must broadcast to `x` with `axis` set to 1", {
diff --git a/tests/testthat/test-slice.R b/tests/testthat/test-slice.R
index f532323a..ad1d4083 100644
--- a/tests/testthat/test-slice.R
+++ b/tests/testthat/test-slice.R
@@ -420,6 +420,23 @@ test_that("`rray_slice_axis()` keeps titles", {
   )
 })
 
+test_that("`axis` can be a title", {
+  x <- array(
+    1:6,
+    c(2L, 3L),
+    dimnames = list(row = c("a", "b"), col = c("c", "d", "e"))
+  )
+
+  expect_identical(
+    rray_slice_axis(x, 1L, axis = "col"),
+    rray_slice_axis(x, 1L, axis = 2)
+  )
+  expect_identical(
+    rray_slice_axis(x, c("e", "c"), axis = "col"),
+    rray_slice_axis(x, c(3L, 1L), axis = 2)
+  )
+})
+
 test_that("`rray_slice_axis()` works with a bare vector", {
   expect_identical(
     rray_slice_axis(c(a = 1L, b = 2L), c(2L, 1L), axis = 1),
@@ -457,6 +474,7 @@ test_that("`axis` is validated", {
     rray_slice_axis(x, 1L, axis = 3)
     rray_slice_axis(x, 1L, axis = c(1, 2))
     rray_slice_axis(x, 1L, axis = NA_integer_)
+    rray_slice_axis(x, 1L, axis = "row")
   })
 })
 
@@ -986,6 +1004,23 @@ test_that("`rray_slice_assign_axis()` keeps titles", {
   )
 })
 
+test_that("`axis` can be a title in `rray_slice_assign_axis()`", {
+  x <- array(
+    1:6,
+    c(2L, 3L),
+    dimnames = list(row = c("a", "b"), col = c("c", "d", "e"))
+  )
+
+  expect_identical(
+    rray_slice_assign_axis(x, 1L, axis = "col", value = 0L),
+    rray_slice_assign_axis(x, 1L, axis = 2, value = 0L)
+  )
+  expect_identical(
+    rray_slice_assign_axis(x, c("e", "c"), axis = "col", value = 0L),
+    rray_slice_assign_axis(x, c(3L, 1L), axis = 2, value = 0L)
+  )
+})
+
 test_that("reports subscript errors from `rray_slice_assign_axis()` as `i`", {
   x <- array(1:6, c(2L, 3L), dimnames = list(c("a", "b"), NULL))
 
@@ -1000,6 +1035,7 @@ test_that("`axis` and `value` are validated by `rray_slice_assign_axis()`", {
 
   expect_snapshot(error = TRUE, {
     rray_slice_assign_axis(x, 1L, axis = 3, value = 0L)
+    rray_slice_assign_axis(x, 1L, axis = "row", value = 0L)
     rray_slice_assign_axis(x, 1L, axis = 1, value = "a")
     rray_slice_assign_axis(x, 1L, axis = 1, value = 1:2)
   })
diff --git a/tests/testthat/test-split.R b/tests/testthat/test-split.R
index 89fcca5c..112c2982 100644
--- a/tests/testthat/test-split.R
+++ b/tests/testthat/test-split.R
@@ -185,6 +185,14 @@ test_that("names on non-split axes are kept", {
   expect_identical(dimnames(out[[3]]), list(c("a", "b"), "z"))
 })
 
+test_that("`axis` can be a title", {
+  x <- array(1:6, c(2, 3), dimnames = list(row = NULL, col = c("x", "y", "z")))
+  expect_identical(
+    rray_split(x, axis = "col", dimensions = c(2, 1)),
+    rray_split(x, axis = 2, dimensions = c(2, 1))
+  )
+})
+
 test_that("names on the split axis are sliced", {
   x <- array(1:6, c(2, 3), dimnames = list(c("a", "b"), c("x", "y", "z")))
 
@@ -307,6 +315,7 @@ test_that("`axis` is validated", {
     error = TRUE
   )
   expect_snapshot(rray_split(x, axis = 1.5, dimensions = 1), error = TRUE)
+  expect_snapshot(rray_split(x, axis = "row", dimensions = 1), error = TRUE)
   expect_snapshot(
     rray_split(x, axis = structure(1L, class = "foo"), dimensions = 1),
     error = TRUE
diff --git a/tests/testthat/test-titles.R b/tests/testthat/test-titles.R
index 52ee466c..aed11cc0 100644
--- a/tests/testthat/test-titles.R
+++ b/tests/testthat/test-titles.R
@@ -127,6 +127,21 @@ test_that("title setters remove one or all titles", {
   expect_identical(dimnames(out), unname(dimnames(x)))
 })
 
+test_that("`rray_set_axis_title()` takes a title for `axis`", {
+  x <- matrix(
+    1:6,
+    2,
+    3,
+    dimnames = list(Row = c("a", "b"), Column = c("x", "y", "z"))
+  )
+
+  out <- rray_set_axis_title(x, "Row", "R")
+  expect_identical(rray_titles(out), c("R", "Column"))
+
+  out <- rray_set_axis_title(x, "Column", NULL)
+  expect_identical(rray_titles(out), c("Row", ""))
+})
+
 test_that("title setters keep empty titles", {
   x <- matrix(
     1:6,
@@ -166,6 +181,7 @@ test_that("title getters reject invalid input and axes", {
   expect_snapshot(rray_axis_title(x, 3), error = TRUE)
   expect_snapshot(rray_axis_title(x, NA_integer_), error = TRUE)
   expect_snapshot(rray_axis_title(x, c(1, 2)), error = TRUE)
+  expect_snapshot(rray_axis_title(x, "Row"), error = TRUE)
 })
 
 test_that("title setters reject invalid input and values", {
@@ -176,6 +192,7 @@ test_that("title setters reject invalid input and values", {
   expect_snapshot(rray_set_titles(x, 1:2), error = TRUE)
   expect_snapshot(rray_set_titles(x, "Row"), error = TRUE)
   expect_snapshot(rray_set_axis_title(x, 0, "Row"), error = TRUE)
+  expect_snapshot(rray_set_axis_title(x, "Row", "R"), error = TRUE)
   expect_snapshot(rray_set_axis_title(x, 1, 1L), error = TRUE)
   expect_snapshot(rray_set_axis_title(x, 1, character()), error = TRUE)
   expect_snapshot(rray_set_axis_title(x, 1, c("Row", "Column")), error = TRUE)
diff --git a/tests/testthat/test-unstack.R b/tests/testthat/test-unstack.R
index b657d279..b604d0e5 100644
--- a/tests/testthat/test-unstack.R
+++ b/tests/testthat/test-unstack.R
@@ -74,6 +74,11 @@ test_that("names on the axis become the list names", {
   expect_identical(out$x, array(1:2, 2, dimnames = list(c("a", "b"))))
 })
 
+test_that("`axis` can be a title", {
+  x <- array(1:6, c(2, 3), dimnames = list(row = NULL, col = c("x", "y", "z")))
+  expect_identical(rray_unstack(x, axis = "col"), rray_unstack(x, axis = 2))
+})
+
 test_that("names on the surviving axes move to their new locations", {
   x <- array(
     1:24,
@@ -184,6 +189,7 @@ test_that("`axis` is validated", {
   expect_snapshot(rray_unstack(x, axis = c(1, 2)), error = TRUE)
   expect_snapshot(rray_unstack(x, axis = NA_integer_), error = TRUE)
   expect_snapshot(rray_unstack(x, axis = 1.5), error = TRUE)
+  expect_snapshot(rray_unstack(x, axis = "row"), error = TRUE)
   expect_snapshot(
     rray_unstack(x, axis = structure(1L, class = "foo")),
     error = TRUE