Overlay plots in R

Question

I want to plot 3 barplots together in one graph based on values from different columns of a data frame.

It should look something like this .

The y-values of plot 1 are the sum of the y-values of plot 2 and 3. The color of plot 1 and 2 can be fully filled (eg blue & red), but the color of plot 3 has to be translucent.

I was able to make a plot for each column separately using the barplot() function, but I was not able to combine them in one graph.

barplot(covpatient[[1]]$cov, names.arg = covpatient[[1]]$exon, xlab = covpatient[[1]]$gene[1] , ylab = "read depth" , border = "blue", col = "blue")
barplot(covpatient[[1]]$plus, names.arg = covpatient[[1]]$exon, xlab = covpatient[[1]]$gene[1] , ylab = "read depth" , border = "red", col = "red")
barplot(covpatient[[1]]$min, names.arg = covpatient[[1]]$exon, xlab = covpatient[[1]]$gene[1] , ylab = "read depth" , border = "gray", col = "gray")

Could someone give me a hand?

Answer 1

I'm not exactly sure if this is what you want... but based on the graphic that you sent I think this will help:

require(ggplot2)
require(reshape2)

covpatient <-list()
covpatient$cov <-rnorm(100,2)
covpatient$plus <-rnorm(100,4)
covpatient$min <-rnorm(100,1)

plot_covpatient <- do.call(rbind,covpatient) 

melted_plot_covpatient<-melt(plot_covpatient,value.name = 'Value')

ggplot(melted_plot_covpatient,aes(group=Var1))+
  geom_density(aes(Value,colour=Var1,fill=Var1),alpha=.5)