Changing y axis text on mcmc_areas() plot from bayesplot R package

Question

I am having some trouble altering the y-axis values in graphs produced by the mcmc_areas function. My goal is to change the text and update the y-axis values to include greek, subscripted letters. I can do this pretty easily in other graphs that can be created using the bayesplot package in R.

For instance:

#I pull out my posterior draws
posterior<-as.matrix(fit.lv2)

#I grab just the parameters of interest for the moment
gamma.b0<-posterior[,c('gamma[1,1]',
                       'gamma[1,2]',
                       'gamma[1,3]',
                       'gamma[1,4]')]

#I rename the columns 
colnames(gamma.b0)<-c('Intercept~(gamma[0][0])',
                      'DN~(gamma[0][1])',
                      'Pos~Events~(gamma[0][2])', 
                      'Neg~Events~(gamma[0][4])')

#And finally I plot the posterior density for each parameter of interest
b0.g1<-mcmc_dens(gamma.b0, facet_args = list(labeller=ggplot2::label_parsed))

which produces:

So far so good. But what I cannot figure out is how to get the plot to reproduce this same text using the mcmc_areas() function. I have tried yaxis_text and yaxis_ticks neither of which seem to work the way I want to update the values on the y axis. I either get warnings or some version of the mcmc_areas plot with the column name reproduced exactly (which is far from the aesthetic I am going for):

Any thoughts or suggestions are much appreciated.

Data is below:

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0.113504166406202, 0.0691274320090004), .Dim = c(250L, 4L), .Dimnames = structure(list(
    iterations = NULL, parameters = c("Intercept~gamma[0][0]", 
    "DN~gamma[0][1]", "Pos~Events~gamma[0][2]", "Neg~Events~gamma[0][4]"
    )), .Names = c("iterations", "parameters")))

Answer 1

You need to add scale_y_discrete and there you map the existing labels, which are just "Intercept~gamma[0][0]" to expressions. A little bit of effort, but it works.

For the mentioned example it would work like this:

library("ggplot2")
library("bayesplot")

mcmc_areas(gamma.b0) +  scale_y_discrete(labels=c(
  "Intercept~gamma[0][0]" = expression(paste("Intercept~",gamma[0][0])), 
  "DN~gamma[0][1]" =  expression(paste("DN~",gamma[0][1])),
  "Pos~Events~gamma[0][2]" = expression(paste("Pos~Events~",gamma[0][2])), 
  "Neg~Events~gamma[0][4]" = expression(paste("Neg~Events~",gamma[0][4]))
  ))

The gamma.b0 was taken from the dput of the question starter.

Will look like this then:

And just ignore the Scale for 'y' is already present warning. It just informs you, that you are overwriting the scale. But, well that is what we want to. If we had full control we of course would just replace the first call to scale_y, but as it is somewhere hidden in the package, we have to overwrite it.

Answer 2

It is a ggplot object, so you can do mcmc_areas(...) + ggplot2::scale_y_discrete(labels = c("foo", "bar"))