Pretty ridges plot for stan parameters

param_ridges.R

# Pretty ridges plot for stan parameters
# MIT license (c) Erik-Jan van Kesteren 2018
# WARNING: sourcing this function will install/update packages

if (requireNamespace("devtools", quietly = TRUE)) {
  suppressMessages(devtools::install_github("vankesteren/firatheme"))
  suppressMessages(devtools::install_cran(c("dplyr", "tidyr", "forcats", 
                                            "ggplot2", "ggridges")))
  param_ridges <- function(stanfit, params, ...) {
    stopifnot(class(stanfit) == "stanfit")
    # create df
    df <- dplyr::bind_rows(lapply(stanfit@sim$samples, dplyr::as_tibble))
    df <- tidyr::gather(data = df, key = "parameter", value = "samples")
    df <- dplyr::mutate(df, paramname = as.factor(
      gsub(x = parameter, pattern = "\\[[0-9]+\\]", replacement = "", perl = TRUE)
    ))
    if (!missing(params)) {
      df <- dplyr::filter(df, paramname %in% params)
      df$paramname <- forcats::fct_drop(df$paramname)
      df$paramname <- forcats::fct_relevel(df$paramname, rev(params))
      df <- dplyr::arrange(df, paramname)
      df$parameter <- forcats::as_factor(df$parameter)
    }
    ggplot2::ggplot(df, ggplot2::aes(samples, parameter, fill = paramname)) + 
      ggridges::geom_density_ridges2(alpha = 0.6, ...) +
      firatheme::theme_fira() + 
      ggplot2::theme(legend.position = "none") +
      ggplot2::labs(x = "Parameter value", y = "")
  }
} else {
  warning("Package devtools needed for this function, install it first!")
}