Heatmap

library(gplots)
col = redgreen(100)

heatmap(as.matrix(USJudgeRatings),Colv=NA,col=col)

• Draw horizontal or vertial line in heatmap

  library(gplots)
  data(mtcars)
  x  <- as.matrix(mtcars)
  heatmap.2(x, trace='none',Rowv=F,Colv=F, add.expr=c(abline(h=c(2,3,4)), mtext(side=2,text='text')))