Question

Hi can I add an additional legend to a ggplot.
Like
the following code

d <- melt(as.matrix(data.frame(y1=1/(1:10),y2=1/(10:1))))
ggplot(d, aes(x=Var1, y=value,fill=Var2)) + geom_bar(stat="identity",position='dodge')

This generates a nice legend containing the name of my dataframe.
But is it possible to put in an extralegend, that contains some extra information generated from the data.

In the standard R, I would add the additional legend like

d<-data.frame(y1=1/(1:10),y2=2*1/(10:1))
barplot(t(d),beside=T)
legend("top",paste("sums:",apply(d,2,sum)))

Thanks

Answer 1

This seems to work for me.

    plot.new()
    d <- melt(as.matrix(data.frame(y1=1/(1:10),y2=1/(10:1))))
    ggplot(d, aes(x=Var1, y=value,fill=Var2)) + 
    geom_bar(stat="identity",position='dodge')

then the exciting stuff.

  legend('top',paste("sums:",tapply(d$value,d$Var2,sum)))

I changed the apply statement to work on the molten data.

I am not aware of a ggplot solution, but I would love to see one.