Hello,

I’m trying to change colors of posterior parameter distribution, for which estimation was done through brms. I use mcmc_areas() function of bayesplot package https://mc-stan.org/bayesplot/reference/MCMC-intervals.html. This function shows distributions of each distribution vertically, with the same color (the default is light blue). I would like to change this color manually with variation by distributions. For example, the top distribution is red, the second is blue, and so on. I added scale_color_manual(values = c(“red”, "blue”)). But it did not work.

```
mcmc_areas(
as.array(model1),
pars = c("b_A", "b_B"),
prob = 0.8,
prob_outer = 0.95,
point_est = "median") +
ggplot2::labs(title = "Posterior parameter distributions") +
scale_color_manual(values = c("red", "blue"))
```

I find this way to change color https://discourse.mc-stan.org/t/bayesplot-mcmc-areas-line-and-fill-colour/26919/2. But it changes colors of all distributions consistently.

Do someone know the way to hack the color of distributions?

Thank you.

Not exactly a hack since it will take you a bit of work but you can generate plots one parameter at a time with different color scheme (& store them in a list) and then assemble the plots into one graphic. I use patchwork and `patchwork::wrap_plots`

for this. I imagine it could work especially well if the parameters are grouped by category (location params, scale params, …) and you use different colors for each category.

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Thank you very much. It’s a very great idea. I tried such way. But I have a problem yet. The patchwork function generates each distribution in each panel. So I modified your idea like the following. It fixes the range of x-axis across panels and deletes x-axes of all panels other than the bottom panel. I use cowplot package instead of patchwork package, just for my familiarity. Thank you!!!

```
p <- list()
parameter_vec <- c("b_a", "b_b", "b_c")
color_vec <- c("gray", "blue", "red")
for (i in 1:length(parameter_vec)){
color_scheme_set(color_vec[i])
p[[i]] <- mcmc_areas(
as.array(model1),
pars = c(parameter_vec[i]),
prob = 0.8,
prob_outer = 0.95,
point_est = "median") +
scale_y_discrete(labels = c(name_levels[i])) +
scale_x_continuous(limits = c(-0.5, 1.5))
if (i != 3){
p[[i]] <- p[[i]] +
theme(axis.ticks.x = element_blank(),
axis.text.x = element_blank(),
axis.title.x = element_blank(),
axis.line.x = element_blank())
}
}
cowplot::plot_grid(p[[1]], p[[2]], p[[3]],
align = "hv",
ncol = 1)
```

1 Like