The function produces the plot of the table()
function with colour densities
corresponding to the respective frequencies of appearance. If the value appears more
often than the other (e.g. 0.5 vs 0.15), then it will be darker. The frequency of 0
corresponds to the white colour, the frequency of 1 corresponds to the black.
See details in the vignette "Marketing analytics with greybox":
vignette("maUsingGreybox","greybox")