Side-by-side bars in bar plot

Question

This is based on this post. Suppose that I have this data:

y = data.frame(Specie=c(\'A\',\'V\',\'R\',\'P\',\'O\'),Number=c(18756,8608,3350,3312,1627))
z = data.         


        

Answer 1

y = data.frame(Specie=c('A','V','R','P','O'),Number=c(18756,8608,3350,3312,1627))
z = data.frame(Specie=c('A','V','R','P','O'),Number=c(17000,1000,8000,5500,9000))

library("ggplot2")
library("reshape2")

df=merge(y,z,by=c("Specie"))
names(df)=c("Specie","y","z")

df=melt(df)

ggplot(df,aes(x=Specie,y=value,fill=variable))+geom_bar( stat="identity",position=position_dodge())