R/gg_reshist.R

In yeukyul/lindia: Automated Linear Regression Diagnostic

#' Generate histogram of residuals in ggplot.
#'
#' @param fitted.lm a fitted linear model (i.e. lm, glm) that contains fitted regression
#' @param bins bin size for histogram
#' @return A ggplot object
#' @examples
#' library(MASS)
#' data(Cars93)
#' cars_lm <- lm(Price~ Passengers + Length + RPM, data = Cars93)
#' gg_reshist(cars_lm)
#' # specify number of bins
#' gg_reshist(cars_lm, bins = 20)
#' @export
#'
gg_reshist <- function(fitted.lm, bins = NULL) {

   handle_exception(fitted.lm, "gg_reshist")

   #obtain residual and fitted values from fitted.lm
   res = data.frame(residuals = residuals(fitted.lm))

   if (is.null(bins)) {
      return (ggplot(data = res, aes(x = residuals)) + geom_histogram(color = "white") +
                 ggtitle("Histogram of Residuals") +
                 labs(x = "Residuals"))
   }
   else {
      return (ggplot(data = res, aes(x = residuals)) + geom_histogram(color = "white", bins = bins) +
                 ggtitle("Histogram of Residuals") +
                 labs(x = "Residuals", y = "Count"))
   }

}