plot_dissimilarity: a plot for displaying dissimilarity distances of subgroups
In SubgrPlots: Graphical Displays for Subgroup Analysis in Clinical Trials

this function produces a plot for displaying dissimilarity distances of pairwise subgroups, where dissmiliarity distance is defined by 1 - |intersect(A, B)|/|A|, for any sets A and B and A is the baseline set. The horizontal axis represents dissimilarity distance. The letters represent subgroups defined by the categories of the selected covariates. The letter above the green triangle is the baseline for calculating dissimilarity distances with the others above the red cross. There are two modes of display - one is that subgroup letters are located at the exact dissimilarity distance; the other is that letters are located at the middle of the category of dissimilarity distances. Note that some dissimilarity distances are known (such as 0 and 1) and therefore they are not shown in the graphical display. Also, the range of dissimilarity distances can be adjusted.

plot_dissimilarity(
  dat,
  covari.sel,
  mode,
  range.ds = c(0, 1),
  font.size = c(1, 0.9, 1, 0.7),
  title = NULL,
  lab.x = NULL
)

`dat`	a data set
`covari.sel`	a vector of indices of covariates
`mode`	a value specifying the type of display; either 1 or 2.
`range.ds`	a vector specifying the range of the dissimilarity distance
`font.size`	a vector specifying the size of labels and text; the first element is for the title; the second is for the x-axis label; the third is for the labels of baseline subgroups; the fourth is for the remaining subgroup labels (except for the baseline subgroup).
`title`	a string specifying the main titles.
`lab.x`	a string specifying the x-axis label.

data(prca)
dat <- prca

## 1. dissimilarity plot ----------------------------------------------------
plot_dissimilarity(dat = dat,
                   covari.sel = c(4,5,6),
                   mode = 3,
                   range.ds = c(0,1),
                   font.size = c(1, 0.9, 1, 0.7),
                   title = NULL,
                   lab.x = "Dissimilarity distance")