The “stan_hist” Function in R

• Package: rstan

• Purpose: Histogram plotting for Stan model diagnostics.

• General class: Visualization

• Required argument(s):

• object: Stanfit object from which to extract samples for plotting.

• Notable optional arguments:

• pars: A character vector specifying the parameters to plot. If not specified, all parameters are plotted.

• ...: Additional arguments passed to the plotting function.

• Example:

• # Load the rstan package
  library(rstan)
  
  # Fit a simple linear regression model
  model_code <- "
  data {
  int<lower=0> N;
  vector[N] x;
  vector[N] y;
  }
  parameters {
  real alpha;
  real beta;
  real<lower=0> sigma;
  }
  model {
  y ~ normal(alpha + beta * x, sigma);
  }
  "
  model_data <- list(N = 100, x = rnorm(100), y = rnorm(100))
  fit <- stan(model_code = model_code, data = model_data, chains = 4)
  
  # Plot the histogram of the alpha parameter
  stan_hist(fit, pars = "alpha")

• This example demonstrates how to use the stan_hist function from the rstan package to plot a histogram of a parameter (alpha in this case) extracted from a Stan model (fit). The function takes the Stan object fit as the x argument and allows optional arguments (...) to be passed to customize the plot.