A heatmap example
heatmap'data.frame': 144 obs. of 5 variables: $ Var1 : Factor w/ 9 levels "a","b","c","d",..: 1 2 3 4 5 6 7 8 9 1 ... $ Var2 : Factor w/ 16 levels "A","B","C","D",..: 1 1 1 1 1 1 1 1 1 2 ... $ value: num -0.622 0.271 0.563 2.426 3.788 ... $ X1 : Factor w/ 9 levels "b","a","d","c",..: 2 1 4 3 5 6 7 8 9 2 ... $ X2 : Factor w/ 16 levels "P","O","M","I",..: 13 13 13 13 13 13 13 13 13 14 ...