Les laboratoires remplissent ggplot2
df <- data.frame(x=1:10,group=c(rep("a",5),rep("b",5)))
legend_title <- "OMG My Title"
ggplot(df, aes(x=x, fill=group)) + geom_density(alpha=.3) +
scale_fill_manual(legend_title,values=c("orange","red"))
MF