R code used to produce the graph shown below.


library(plotrix) 
par(mar = c(0.5, 2, 3.5, 2)) 
widedf<-data.frame(ID=c(1, 2), 
                   time1=c(10,11), 
                   time2=c(20,21), 
                   time3=c(30,31)) 
longdf <- melt(widedf, id.vars=c("ID")) 
longdf$variable <- c(1,1,2,2,3,3) 
 
 
 
headers <- c("gray", col.tint("blue", .5), col.tint("blue", .6), col.tint("blue", .7)) 
cellcol <- matrix(c(headers, col.tint(headers, .5)), nrow=2, byrow=TRUE) 
 
color2D.matplot(widedf, 
                show.values = TRUE, 
                axes = FALSE, 
                xlab = "", 
                ylab = "", 
                vcex = 2.5, 
                vcol = "black", cellcolor=cellcol) 
 
axis(3, at = seq_len(ncol(widedf)) - 0.5, 
     labels = names(widedf), tick = FALSE, cex.axis = 2.2)