Rで行列の各数値要素の大小を濃淡で表したい場合

library(lattice)

# 10 x 10 の行列を作る

my.nrow = 10
my.ncol = 10
set.seed(123)  # sample() で取得する乱数の種を与える
my.mat <- matrix(data = sample(1:100, my.nrow*my.ncol, replace = TRUE),
                 nrow = my.nrow, 
                 ncol = my.ncol)
xmin <- min(my.mat)
xmax <- max(my.mat)

# Build the plot
pal <- colorRampPalette(c("lightblue", "blue"), space = "rgb")

levelplot(my.mat, main = "10 X 10 Levelplot", xlab = "", ylab = "",
          col.regions = pal(20), cuts = 20, 
          at = seq(from = xmin, to = xmax, by = (xmax-xmin)/20) )