R/beta_plot.R

In softloud/parameterpal: Intepretable parameters for the beta distribution

#' Plot beta distribution
#'
#' This function utlises [beta_pal] to produce a visualisation of the beta
#' distribution, with user-specified interpretable conditions.
#'
#'
#' @inheritParams beta_pal
#' @param caption_width Option to control the width of the caption, defaults to
#' 70.
#' @param theme_default Currently defaults to `ggthemes::theme_tufte`.
#'
#' @export

beta_plot <- function(expected_value,
                      within,
                      this_much,
                      caption_width = 70,
                      theme_default = TRUE) {
  # calculate parameters
  par <-
    beta_pal(expected_value = expected_value,
             within = within,
             this_much = this_much)

  # return plot of beta distribution with parameters
  tibble::tibble(x = c(0, 1)) %>%
    ggplot2::ggplot(ggplot2::aes(x = x)) +

    # desired quantiles
    ggplot2::geom_rect(
      xmin = expected_value - within,
      xmax = expected_value + within,
      ymin = 0,
      ymax = Inf,
      alpha = 0.2
    ) +

    ggplot2::geom_vline(xintercept = expected_value,
                        linetype = "dashed",
                        alpha = 0.8) +
    ggplot2::stat_function(
      fun = dbeta,
      linetype = "dotted",
      args = list(
        shape1 = par$shape1_est,
        shape2 = par$shape2_est
      )
    ) +
    ggplot2::labs(
      title = sprintf("beta(%.1f, %.1f)",
                      par$shape1_est,
                      par$shape2_est),
      y = NULL,
      x = NULL,
      caption = sprintf(
        "Assuming a beta distribution (dotted line), with expected value %g  (vertical dashed line), and %g per cent of falling within %g of %g, parameterpal:: approximates the distribution beta(%g, %g). Parameters in the title are rounded. The shaded region shows the desired region %g per cent of values falling within %g of %g, under the approximated distribution, beta(%g, %g), %g per cent of values fall within this region.",
        expected_value,
        this_much * 100,
        within,
        expected_value,
        par$shape1_est,
        par$shape2_est,
        this_much * 100,
        within,
        expected_value,
        par$shape1_est,
        par$shape2_est,
        (
          pbeta(q = expected_value + within, par$shape1_est, par$shape2_est) -
            pbeta(q = expected_value - within, par$shape1_est, par$shape2_est)
        ) * 100
      ) %>% stringr::str_wrap(width = caption_width)
    ) +
    ggplot2::theme(
      axis.text.y = ggplot2::element_blank(),
      axis.ticks.y = ggplot2::element_blank()
    ) -> bplot

  if (isTRUE(theme_default)) {
    bplot + ggthemes::theme_tufte(base_size = 12) + ggplot2::theme(
      axis.text.y = ggplot2::element_blank(),
      axis.ticks.y = ggplot2::element_blank()
    )

  } else {
    bplot
  }

}