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问题:
I'm having a little trouble with getting ggplot2 to work as I want. Basically, I'd like to compare actual observations vs. approximated by putting them in one single plot. For example,
> library(ggplot2) > df.actual <- data.frame(x = 1:100, y = (1:100) * 2) > df.approx <- data.frame(x = 1:150, y = (1:150) * 2 + 5 + rnorm(150, mean = 3) ) > ggplot() + geom_point(aes(x, y), data = df.actual) + geom_line(aes(x,y), data = df.approx)
My problem is that I can't display a legend. I read somewhere that ggplot2's legend is not very flexible(?). Ideally, a legend with
- title = 'Type'
- key: a black filled point, and a black line
- key label: 'Actual', 'Approximate'
- legend.position = 'topright'
Thanks.
回答1:
Try this to get you started
ggplot() + geom_point(aes(x, y, colour = "actual"), data = df.actual) + geom_line(aes(x, y, colour = "approximate"), data = df.approx) + scale_colour_discrete("Type")
回答2:
This is some kind of hack to modify the legend by manipulation of the grid object:
library("ggplot2") df.actual <- data.frame(x=1:100, y=(1:100)*2) df.approx <- data.frame(x=1:150, y=(1:150)*2 + 5 + rnorm(150, mean=3)) p <- ggplot() + geom_point(aes(x, y, colour="Actual"), data=df.actual) + geom_line(aes(x, y, colour="Approximate"), data=df.approx) + scale_colour_manual(name="Type", values=c("Actual"="black", "Approximate"="black")) library("grid") grob <- ggplotGrob(p) tmp <- grid.ls(getGrob(grob, "key.segments", grep=TRUE, global=TRUE))$name grob <- removeGrob(grob, tmp[1]) # remove first line segment in legend key tmp <- grid.ls(getGrob(grob, "key.points", grep=TRUE, global=TRUE))$name grob <- removeGrob(grob, tmp[2]) # remove second point in legend key grid.draw(grob)
ggplot2 output http://img134.imageshack.us/img134/8427/ggplotlegend.png
