gghdr provides the framework to visualize Highest Density Regions (HDR) with the grammar of graphics as implemented in
ggplot2. There are several statistical methods (viz. box plots, summary plots or letter value plots) to summarize a distribution by region of the sample space covering certain probability. The method of summarizing a distribution using HDR are useful for plotting multimodal distributions. HDR may include disjoint subsets each covering a local mode.