density_bins: Density bins and histogram bins as data frames

Description

Generates a data frame of bins representing the kernel density (or histogram) of a vector, suitable for use in generating predictive distributions for visualization. These functions were originally designed for use with the now-deprecated predict_curve(), and may be deprecated in the future.

Usage

density_bins(x, n = 101, ...)
histogram_bins(x, n = 30, breaks = n, ...)

Arguments

A numeric vector

Number of bins

...

Additional arguments passed to density() or hist().

breaks

Used to set bins for histogram_bins. Can be number of bins (by default it is set to the value of n) or a method for setting bins. See the breaks argument of hist().

Value

A data frame representing bins and their densities with the following columns:

mid

Bin midpoint

lower

Lower endpoint of each bin

upper

Upper endpoint of each bin

density

Density estimate of the bin

Details

These functions are simple wrappers to density() and hist() that compute density estimates and return their results in a consistent format: a data frame of bins suitable for use with the now-deprecated predict_curve().

density_bins computes a kernel density estimate using density().

histogram_bins computes a density histogram using hist().

Examples

Run this code

# NOT RUN {
library(ggplot2)
library(dplyr)
library(purrr)
library(tidyr)

if (
  require("rstanarm", quietly = TRUE) &&
  require("modelr", quietly = TRUE)
) {

  theme_set(theme_light())

  m_mpg = stan_glm(mpg ~ hp * cyl, data = mtcars)

  step = 1
  mtcars %>%
    group_by(cyl) %>%
    data_grid(hp = seq_range(hp, by = step)) %>%
    add_predicted_draws(m_mpg) %>%
    summarise(densities = list(density_bins(.prediction))) %>%
    unnest(densities) %>%
    ggplot() +
    geom_rect(aes(
      xmin = hp - step/2, ymin = lower, ymax = upper, xmax = hp + step/2,
      fill = ordered(cyl), alpha = density
    )) +
    geom_point(aes(x = hp, y = mpg, fill = ordered(cyl)), shape = 21, data = mtcars) +
    scale_alpha_continuous(range = c(0, 1)) +
    scale_fill_brewer(palette = "Set2")
}
# }