Add vignette sections for *_data() companion functions

[ishaan-arora-1]

Fixes #435

Added vignette sections in the PPC and MCMC vignettes demonstrating how to use the *_data() companion functions for building custom ggplot2 visualizations, as requested in the issue.

AI Usage policy :
Parts of the documentation were generated using an llm

[florence-bockting]

Thank you @ishaan-arora-1 for your PR and working on this issue.

I noticed that the checks currently fail as the object 'yrep' in your example code does not exist. Can you please have a look at this?

In general it is a good idea to check whether you can build and render a modified .Rmd document locally. This allows you to catch already some errors. To build all vignettes you can run from the package root: devtools::build_vignettes().

Furthermore, to render the graphical-ppc.Rmd locally you can use for example: rmarkdown::render('vignettes/graphical-ppcs.Rmd', params=list(EVAL=TRUE), output_dir='inst/doc')
(adjust the output directory as needed). When you render the Rmd you will notice the error message.

[ishaan-arora-1]

Thank you @ishaan-arora-1 for your PR and working on this issue.

I noticed that the checks currently fail as the object 'yrep' in your example code does not exist. Can you please have a look at this?

In general it is a good idea to check whether you can build and render a modified .Rmd document locally. This allows you to catch already some errors. To build all vignettes you can run from the package root: devtools::build_vignettes().

Furthermore, to render the graphical-ppc.Rmd locally you can use for example: rmarkdown::render('vignettes/graphical-ppcs.Rmd', params=list(EVAL=TRUE), output_dir='inst/doc') (adjust the output directory as needed). When you render the Rmd you will notice the error message.

Thanks a lot for catching that. The vignette defines yrep_poisson and yrep_nb but never a bare yrep and I should have caught that before pushing. il fix the pr, ill do as youve instructed. and i'll ask for a re-review once im done!!