R, how can I make a heatmap out of a simple matrix? [duplicate]

Question

Say I have a simple matrix A generated by

 A = matrix(c(1,2,3,4,5,6,7,8,9),nrow=3,ncol=3)

Now, my goal is to make a heatmap out of A, such that each number is replaced by a colour field. How to do that? I tried

heatmap(A)

but it produced three coloured stripes instead of 9 distinct fields.

Answer 1

One of the possibilities that have not been described in the solutions referred to in the comments consists in using the pheatmap package:

library(pheatmap)
A <- matrix(c(1,2,3,4,5,6,7,8,9),nrow=3,ncol=3)
pheatmap(A, cluster_rows = FALSE, cluster_cols = FALSE)

which gives: