@@ -324,15 +324,28 @@ regression effects will result in an improper posterior distribution.
324324Hence, a proper prior is required to avoid improper posteriors in case
325325of separation.
326326
327- In the examples above we used a very flat but proper prior With a more
328- informative prior, the autocorrelations of the draws are lower. This can
329- be seen in the next figure, where the simulated data under
330- quasi-separation are re-analyzed with a Normal prior that is tighter
331- around zero.
327+ We now analyse the data under the more informative prior,
328+ \$ \Normal(\mathbf{0}, \mathbf{I}}\$ . With this prior we assume that both
329+ $P(y = 1)$ and $P(y = 0)$ have a prior probability of $\approx 0.95$ to
330+ be in the interval $\lbrack 0.023,0.977\rbrack$.
332331
333332``` r
333+ set.seed(1234 )
334334betas.sep1 <- probit(y , X.sep , b0 = 0 , B0 = 1 )
335335
336+ res_betas.sep1 <- t(apply(betas.sep1 , 2 , res.mcmc ))
337+ knitr :: kable(round(res_betas.sep1 , 3 ))
338+ ```
339+
340+ | | 2.5% | Posterior mean | 97.5% |
341+ | :------| -------:| ---------------:| -------:|
342+ | | -2.853 | -2.352 | -1.921 |
343+ | x.sep | 4.211 | 4.883 | 5.622 |
344+
345+ In this case the autocorrelations are much lower and the effective
346+ sample sizes are roughly 700.
347+
348+ ``` r
336349par(mfrow = c(2 , 2 ), mar = c(2.5 , 1.5 , 1.5 , .1 ), mgp = c(1.5 , .5 , 0 ), lwd = 1.5 )
337350
338351plot(betas.sep1 [, 1 ], type = " l" , main = " " , xlab = " " , ylab = " " )
@@ -342,7 +355,7 @@ plot(betas.sep1[, 2], type = "l", main = "", xlab = "", ylab = "")
342355acf(betas.sep1 [, 2 ])
343356```
344357
345- ![ ] ( Chapter08_files/figure-html/unnamed-chunk-18 -1.png )
358+ ![ ] ( Chapter08_files/figure-html/unnamed-chunk-19 -1.png )
346359
347360``` r
348361
@@ -864,7 +877,7 @@ qqplot(res1$alpha.post, res2$alpha.post, xlab = "Full Gibbs",
864877abline(a = 0 , b = 1 )
865878```
866879
867- ![ ] ( Chapter08_files/figure-html/unnamed-chunk-36 -1.png )
880+ ![ ] ( Chapter08_files/figure-html/unnamed-chunk-37 -1.png )
868881
869882## Section 8.3: Beyond i.i.d. Gaussian error distributions
870883
@@ -882,7 +895,7 @@ plot(starsCYG, pch = 19, xlim = c(3, 5), ylim = c(3, 7),
882895 xlab = " log temperature" , ylab = " log light intensity" )
883896```
884897
885- ![ ] ( Chapter08_files/figure-html/unnamed-chunk-37 -1.png )
898+ ![ ] ( Chapter08_files/figure-html/unnamed-chunk-38 -1.png )
886899
887900The four giant stars which can also be identified in the scatter plot
888901have the following indices in the data set:
@@ -934,7 +947,7 @@ lines(xnew, preds_subset[, "lwr"], lty = 2)
934947lines(xnew , preds_subset [, " upr" ], lty = 2 )
935948```
936949
937- ![ ] ( Chapter08_files/figure-html/unnamed-chunk-40 -1.png )
950+ ![ ] ( Chapter08_files/figure-html/unnamed-chunk-41 -1.png )
938951
939952### Example 8.11: Star cluster data - heteroskedastic regression analysis with known outliers
940953
@@ -1027,7 +1040,7 @@ lines(xnew, apply(pred_hetero, 1, quantile, 0.025), lty = 2)
10271040lines(xnew , apply(pred_hetero , 1 , quantile , 0.975 ), lty = 2 )
10281041```
10291042
1030- ![ ] ( Chapter08_files/figure-html/unnamed-chunk-45 -1.png )
1043+ ![ ] ( Chapter08_files/figure-html/unnamed-chunk-46 -1.png )
10311044
10321045### Example 8.14: Star cluster data - regression analysis with Gaussian two-component mixture errors
10331046
@@ -1107,7 +1120,7 @@ lines(xnew, apply(preds_mix_1, 1, quantile, 0.025), lty = 2)
11071120lines(xnew , apply(preds_mix_1 , 1 , quantile , 0.975 ), lty = 2 )
11081121```
11091122
1110- ![ ] ( Chapter08_files/figure-html/unnamed-chunk-50 -1.png )
1123+ ![ ] ( Chapter08_files/figure-html/unnamed-chunk-51 -1.png )
11111124
11121125We now assume that the indices of the giant stars are not known. We only
11131126assume that a two-component mixture is used as weight distribution where
@@ -1186,7 +1199,7 @@ lines(xnew, apply(preds_mix_2, 1, quantile, 0.025), lty = 2)
11861199lines(xnew , apply(preds_mix_2 , 1 , quantile , 0.975 ), lty = 2 )
11871200```
11881201
1189- ![ ] ( Chapter08_files/figure-html/unnamed-chunk-53 -1.png )
1202+ ![ ] ( Chapter08_files/figure-html/unnamed-chunk-54 -1.png )
11901203
11911204Finally, we visualize again the mean and the 95%-HPD region together
11921205with the data points for the three modeling approaches: (1) a
@@ -1212,7 +1225,7 @@ lines(xnew, apply(preds_mix_2, 1, quantile, 0.025), lty = 2)
12121225lines(xnew , apply(preds_mix_2 , 1 , quantile , 0.975 ), lty = 2 )
12131226```
12141227
1215- ![ ] ( Chapter08_files/figure-html/unnamed-chunk-54 -1.png )
1228+ ![ ] ( Chapter08_files/figure-html/unnamed-chunk-55 -1.png )
12161229
12171230The plot indicates that all three modeling approaches result in a fit
12181231that is robust to the outlying observations.
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