R: How do I put two box plots next to each other, keeping same y-range for both?

Question

Let's say I have two data sets, one with y-range [min0:max0] and the other with y-range [min1:max1]. How can put both box plots in one plot next to each other with a sane y-range [min(min0, min1):max(max0, max1)]?

Here's what I tried:

d0 <- matrix(rnorm(15), ncol=3)
d1 <- matrix(rnorm(15), ncol=3)

par(mfrow = c(1, 2))
boxplot(d0)
usr <- par("usr")
plot.new()
par(usr = usr)
boxplot(d1, add = TRUE)

But that will only keep the first plots y-range and also squeeze both plots whereas I'd like them to be square.

Any ideas?

Your code is not reproducible. See http://stackoverflow.com/questions/5963269/how-to-make-a-great-r-reproducible-example — Roman Luštrik, Jul 21 '11 at 10:03

Ari B. Friedman · Accepted Answer · 2011-07-21T13:48:52.027

43

d0 <- matrix(rnorm(15), ncol=3)
d1 <- matrix(rnorm(15), ncol=3)

# Using base R graphics
lmts <- range(d0,d1)

par(mfrow = c(1, 2))
boxplot(d0,ylim=lmts)
boxplot(d1,ylim=lmts)

base graphics plot

You may also want to think about a way to do this using grid graphics, either by the lattice or ggplot2 packages.

Here's one attempt in ggplot2:

# Using ggplot2
library(ggplot2)
d <- data.frame(d.type=c(rep(0,15),rep(1,15)),sub.type=rep(c('A','B','C'),10),val=rnorm(30))

p <- ggplot(d, aes(factor(sub.type), val)) 
p + geom_boxplot() + facet_grid(. ~ d.type)

ggplot2

And in lattice:

# Using lattice
library(lattice)
bwplot(~ val|sub.type+d.type ,d)

lattice plot

Note how the grid-based solutions keep you from ever having to specify limits; you specify structure and the software does the rest.

edited Jul 21 '11 at 13:48

answered Jul 21 '11 at 10:32

Ari B. Friedman

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Hmpf, I probably have read over boxplot's ylim argument. Thanks! – htorque Jul 21 '11 at 10:51
I wish I could give you another +1 for the extensive answer, thanks again! – htorque Jul 21 '11 at 11:36
Nah, a *really* extensive answer would have included slices (lattice), aesthetics (ggplot2), and other ways to make the grid-based graphics look prettier :-) – Ari B. Friedman Jul 21 '11 at 11:54
Err, that's shingles not slices. – Ari B. Friedman Jul 21 '11 at 12:30
`lmts` can be calculated more succinctly via: `lmts <- range(d0,d1)`. – Joshua Ulrich Jul 21 '11 at 13:47
@Joshua Ulrich: Thanks, updated. Sometimes you look back at your own code and just shake your head :-). Path dependence in action. – Ari B. Friedman Jul 21 '11 at 13:49
@gsk: In my case s/sometimes/always. I just saw that line and thought, "there has to be a lazier way to get that result". ;-) – Joshua Ulrich Jul 21 '11 at 13:54
@JU: Yeah, I sort of took the " [min(min0, min1):max(max0, max1)]" from the original question and R-ified it. So as the Perl manual says, it's about being lazy the right way, not about being lazy the way that involves more typing and less thought! – Ari B. Friedman Jul 21 '11 at 14:02

R: How do I put two box plots next to each other, keeping same y-range for both?

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