Dieter Menne
Dieter Menne

Reputation: 10215

Same axis limits vert/hor, fixed aspect, free scaling in facets

To compare the result of multiple medical variables with a very large difference in range I want to create a scatterplot like the one below

-

library(ggplot2)
set.seed(11)
d = rbind(
  data.frame(what = "a", v1 = rnorm(20)+0.2, v2 = rnorm(20)),
  data.frame(what = "b", v1 = rnorm(20, 100, 10)+20, v2 = rnorm(20, 100,10)))

ggplot(d, aes(x = v1, y = v2 )) +
  geom_point() +
  geom_abline(slope = 1) +
  facet_wrap(~what, scales = "free") +
  theme(aspect.ratio = 1) +
  coord_fixed(ratio = 1) + # No effect?
  stat_ellipse()

enter image description here

I am aware of the hard way to get this with precomputed limits. Setting individual axis limits with facet_wrap and scales = "free" in ggplot2

Upvotes: 6

Views: 324

Answers (2)

Simon Woodward
Simon Woodward

Reputation: 2026

If you invisibly plot everything with x and y reversed each facet will have identical x and y axes.

library(ggplot2)
set.seed(11)
d = rbind(
  data.frame(what = "a", v1 = rnorm(20)+0.2, v2 = rnorm(20)),
  data.frame(what = "b", v1 = rnorm(20, 100, 10)+20, v2 = rnorm(20, 100,10)))

ggplot(d ) +
  geom_point(aes(x = v1, y = v2 )) +
  geom_blank(aes(x = v2, y = v1 )) +
  geom_abline(slope = 1) +
  facet_wrap(~what, scales = "free") +
  stat_ellipse(aes(x = v1, y = v2 )) +
  stat_ellipse(aes(x = v2, y = v1 ), alpha=0) 

Upvotes: 1

Dieter Menne
Dieter Menne

Reputation: 10215

I ended up using the solution @baptiste suggested in Setting individual axis limits with facet_wrap and scales = "free" in ggplot2 with a dummy geom_blank. It's not perfect, though, because ggplots insists on using its own ideas about scaling, so the line does not go through the corners.

library(ggplot2)
set.seed(11)
d = rbind(
  data.frame(what = "a", v1 = rnorm(20) + 0.2, v2 = rnorm(20)),
  data.frame(what = "b", v1 = rnorm(20, 100, 10) + 20, v2 = rnorm(20, 100,10)))

drange = do.call(rbind, by(d, d$what, function(x) extendrange(c(x$v1, x$v2))))
dummy = data.frame(what = rownames(drange), v1 = drange[,1], v2 = drange[,2] )

ggplot(d, aes(x = v1, y = v2 )) +
  geom_point() +
  geom_abline(slope = 1) +
  theme(aspect.ratio = 1) +
  coord_fixed(ratio = 1, expand = FALSE) +
  stat_ellipse() +
  geom_blank(data = dummy) +
  facet_wrap(~what, scales = "free")

enter image description here

And here the solution with lattice, which simply does what you ask it to do.

lattice::xyplot(v2~v1|what, data = d, aspect = 1, pch = 16,
                scales = list(relation = "free"),
                panel = function(x,y, ...){
                  lattice::panel.xyplot(x, y, ...) 
                  lattice::panel.abline(a = 0, b = 1)
                },
                prepanel = function(x, y, ...){
                  lim = c(min(x, y), max(x, y))
                  list(xlim = lim, ylim = lim)
                })

enter image description here

Upvotes: 0

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