How to overlay two geom_bar?

Question

I am trying to overlay 2 columns from geom_bar obtained from 2 separate data.frames.

 dEQ lab perc 1 lmP 55.9 2 lmN 21.8 3 Nt 0.6 4 expG 5.6 5 expD 0.0 6 prbN 11.2 7 prbP 5.0 

and

 LMD lab perc 1 lmP 16.8 2 lmN 8.9 3 Nt 0.0 4 expG 0.0 5 expD 0.0 6 prbN 0.0 7 prbP 0.0 

The first chart:

 p <- ggplot(dEQ, aes(lab, perc)) + xlab(xlabel) + ylab(ylabel) + geom_bar(stat="identity", colour="blue", fill="darkblue") + geom_text(aes(vecX, vecYEQ+1.5, label=vecYlbEQ), data=dEQ, size=8.5) + theme_bw() + opts(axis.text.x = theme_text(size = 20, face = "bold", colour = "black")) + opts(axis.text.y = theme_text(size = 20, face = "bold", colour = "black")) + coord_flip() + scale_y_continuous(breaks=c(0,10,20,30,40,50,60), labels=c("0","","20","","40","","60"), limits = c(0, 64), expand = c(0,0)) print(p) 

but I want to rewrite with another geom_bar with data.frame LMD

 ggplot(LMD, aes(lab, perc)) + geom_bar(stat="identity", colour="blue", fill="red", add=T) 

and I want to have a legend.

Answer 1

here is an example:

 p <- ggplot(NULL, aes(lab, perc)) + geom_bar(aes(fill = "dEQ"), data = dEQ, alpha = 0.5) + geom_bar(aes(fill = "LMD"), data = LMD, alpha = 0.5) p 

but I recommend rbind them and draw it, dodging:

 dEQ$name <- "dEQ" LMD$name <- "LMD" d <- rbind(dEQ, LMD) p <- ggplot(d, aes(lab, perc, fill = name)) + geom_bar(position = "dodge")