Add color to legend

Question

I have created the following barplot, but the problem is that the legends doesn't have the right color, and the grids are in front of the bars. I would like to put the right columns in the boxes at the legend, and put the grid behind the bars.

I also would like to put a tick in the bottom of each bar just to identify them

How can I do these features in R?

The r script that I use:

autos_data <- read.table("data.dat", header=T, sep="\t") 

barplot(rep(NA,length(autos_data)),ylim=c(0,max(autos_data)),axes=FALSE)
barplot(t(as.matrix(autos_data)), main=NULL, ylab= "% of Cloud usage", xlab="Input data size (MB)", ylim=c(0,50), beside=TRUE, lwd=1:2, angle=c(45,135), density=seq(5,40,10), col=c("blue","red","black","darkgreen"))
grid(NA, 5, lwd=1,lty=5, col="gray") # grid only in y-direction  

# Place the legend at the top-left corner with no frame
coords="top"
legend(coords, c("WestVirginia","Chicago I","Chicago II","California"), text.col=par("col"), cex=1.2, bty="n", xpd=TRUE, horiz=TRUE, inset=c(0,-.22), angle=c(35,135,45,135), density=seq(5,40,10),col=c("blue","red","black","darkgreen"))

Edit:

dput(autos_data)
structure(list(WestVirginia = c(29L, 29L, 23L, 23L), ChicagoI = c(30L, 
21L, 36L, 26L), ChicagoII = c(39L, 42L, 35L, 46L), California = c(2L, 
8L, 6L, 5L)), .Names = c("WestVirginia", "ChicagoI", "ChicagoII", 
"California"), class = "data.frame", row.names = c("1500", "3000", 
"4500", "6000"))

The data:

West-Virginia   ChicagoI    ChicagoII   California
1500    29  30  39  2
3000    29  21  42  8
4500    23  36  35  6
6000    23  26  46  5

Answer 1

This is an inconsistency of parameter names.

You need to set fill:

legend(coords, c("WestVirginia","Chicago I","Chicago II","California"), text.col=par("col"), 
       cex=1.2, bty="n", xpd=TRUE, horiz=TRUE, inset=c(0,-.22), angle=c(35,135,45,135), 
       density=seq(5,40,10), fill=c("blue","red","black","darkgreen"))

Answer 2

You can compute the legend directly in the barplot call, specifying the arguments via args.legend parameter and the text via legend.text. For the grid, you need to replot the barplot after setting the grid, with white and then the lines so the grid doesn't appear anymore in the lines:

It needs 3 calls of the same barplot but I think it gives you what you want:

# first plot
barplot(t(as.matrix(autos_data)), main=NULL, axes=FALSE, beside=TRUE, col="white", ylab= "% of Cloud usage", xlab="Input data size (MB)", ylim=c(0,50))
# add the grid
grid(NA, 5, lwd=1,lty=5, col="gray") # grid only in y-direction  
# hide the grid with white bars
barplot(t(as.matrix(autos_data)), main=NULL, beside=TRUE, col="white", ylab= "% of Cloud usage", xlab="Input data size (MB)", ylim=c(0,50), add=TRUE)
# plot the density lines, the legend, etc.
barplot(t(as.matrix(autos_data)), main=NULL, axes=FALSE, beside=TRUE, 
        lwd=1:2, angle=c(45,135), density=seq(5,40,10), col=c("blue","red","black","darkgreen"), 
        legend.text=c("WestVirginia","Chicago I","Chicago II","California"), 
        args.legend=list(x="top", y=NULL, bty="n", ncol=4), add=TRUE)