A heatmap is a table of numbers, where you substitute the numbers with colored cells. It gives a visual impact to the matrix, what makes it easier to
understand. R proposes several methods to realize your heatmap. The native heatmap() function should satisfy most of your needs. As usual, ggplot2 also
provides great possibilities. Lastly, using the D3heatmap library allows to easily compute interactive heatmaps. Do not miss it!
Native Heatmap Function
Levelplot function from lattice