可以将position_jitter与position_dodge结合使用吗？

Question

我已经非常喜欢箱形图,其中抖动点覆盖在箱线图上以表示实际数据,如下所示:

set.seed(7)
l1 <- gl(3, 1, length=102, labels=letters[1:3])
l2 <- gl(2, 51, length=102, labels=LETTERS[1:2]) # Will use this later
y <- runif(102)
d <- data.frame(l1, l2, y)

ggplot(d, aes(x=l1, y=y)) + 
  geom_point(position=position_jitter(width=0.2), alpha=0.5) +
  geom_boxplot(fill=NA) 

(当每个框中的数据点数量非常不同时,这些特别有用.)

当我(隐含地)使用position_dodge第二个变量分隔箱图时,我想使用这种技术,例如

ggplot(d, aes(x=l1, y=y, colour=l2)) + 
  geom_point(position=position_jitter(width=0.2), alpha=0.5) +
  geom_boxplot(fill=NA)

但是,我无法弄清楚如何通过colour变量(此处l2)躲避点,并且还会抖动它们.

Answer 1

这是一种手动执行抖动和躲避的方法.

# a plot with no dodging or jittering of the points 
dp <- ggplot(d, aes(x=l1, y=y, colour=l2)) + 
  geom_point(alpha=0.5) +
  geom_boxplot(fill=NA)

# build the plot for rendering
foo <- ggplot_build(dp)
# now replace the 'x' values in the data for layer 1 (unjittered and un-dodged points)
# with the appropriately dodged and jittered points
foo$data[[1]][['x']] <- jitter(foo$data[[2]][['x']][foo$data[[1]][['group']]],amount = 0.2)
# now draw the plot (need to explicitly load grid package)
library(grid)
grid.draw(ggplot_gtable(foo))
# note the following works without explicitly loading grid
plot(ggplot_gtable(foo))