create vertically non-overlapping labels next to boxplot using ggplot2

Question

If want to create a boxplot with overlaid points which are labeled at the right hand side. I tried geom_dl form the directlabels package, but get stuck.

library(ggplot2)
library(directlabels)

set.seed(0)
x <- data.frame(label=LETTERS[1:15], 
                x="a",
                y = rnorm(15))
x$xpos <- as.numeric(x$x) + .25

g <- ggplot(x, aes(x=x, y=y)) + 
  geom_boxplot(width=.4) +
  geom_point(col="blue")

Position labels without overlap control using method last.points.

g + geom_dl(aes(x=xpos, label=label), method = "last.points")

Using method last.qp to avoid overlaps fails.

g + geom_dl(aes(x=xpos, label=label), method = "last.qp")   # fails

Error in approx(df[, x.var], df[, tiebreak.var], xvals) : 
  need at least two non-NA values to interpolate

Any ideas, how to get geom_dl running or achieve proper placemant in another way?

Add-on

Using method last.bumpup as @lukeA suggested below works quite fine. However, some labels are still overlapping. Is there a way to tweak this?

Add-on 2

I think the problem only arises when using a factor with more than one level on x.

set.seed(0)
x <- data.frame(label=LETTERS[1:24], 
                g1 = c("a"),
                g2 = c("a", "b"),
                y = rnorm(24))
x$g1 <- as.factor(x$g1)
x$g2 <- as.factor(x$g2)
x$xpos1 <- as.numeric(x$g1) + .25
x$xpos2 <- as.numeric(x$g2) + .25

The label placement for the first plot is fine. For the second with two levels the overlaps remain.

# one group
ggplot(x, aes(x=g1, y=y)) + 
  geom_boxplot(width=.4) +
  geom_point(col="blue") +
  geom_dl(aes(x=xpos1, label=label), method= "last.bumpup")

Two levels

# two groups
ggplot(x, aes(x=g2, y=y)) + 
  geom_boxplot(width=.4) +
  geom_point(col="blue") +
  geom_dl(aes(x=xpos2, label=label), method= "last.bumpup")

I use directlabels_2015.12.16 and ggplot2_2.1.0.

Mark Heckmann
– Mark Heckmann

2016-04-24 18:45:17 +00:00
Commented Apr 24, 2016 at 18:45 — Mark Heckmann
– Mark Heckmann, Commented Apr 24, 2016 at 18:45
Ah, thanks! My version of directlabels was way out of date

jaimedash
– jaimedash

2016-04-24 19:17:36 +00:00
Commented Apr 24, 2016 at 19:17 — jaimedash
– jaimedash, Commented Apr 24, 2016 at 19:17

lukeA · Accepted Answer · 2016-04-24 10:10:29Z

2

You could use the last.bumpup method, which combines last.points and bumpup (last.bumup <- list("last.points","bumpup")):

g + geom_dl(aes(x=xpos, label=label), method = "last.bumpup")

answered Apr 24, 2016 at 10:10

lukeA

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4 Comments

Mark Heckmann Over a year ago

nice, thanks! However, I still get overlap (see add-on above). Any ideas for this?

lukeA Over a year ago

Strange, there should not be any overlaps. Maybe reduce font size and/or increase the y limits or the device height: g + geom_dl(aes(x=xpos, label=label), method = list("last.bumpup", cex=.8)) + ylim(c(min(x$y), max(x$y)*10)) or

ggsave(tf <- tempfile(fileext = ".png"), g + geom_dl(aes(x=xpos, label=label), method = "last.bumpup") + ylim(c(min(x$y), max(x$y)*15)), dpi = 320, height=12); shell.exec(tf)

Mark Heckmann Over a year ago

Thanks for the code. I figured that the problem only arises when using multiple levels on x (see add-on 2 above). A bug?

lukeA Over a year ago

I don't know. If everything fails, I'd use facets like + facet_wrap(~g2, scales = "free_x") + theme(panel.margin=unit(0, "cm")).

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