在ggplot2中并排横向图例 [英] Side by side horizontal legends in in ggplot2

问题描述

我想让我的ggplot图例并排显示，在符号上方的变量名称下面，因为它们位于

您可以使用 title.hjust像我在问题中所建议的那样将标题转移到中心= 0.5 。但是，经过检查，这样做可能会让读者误解哪些颜色/点指向哪个变量。

I would like to get my ggplot legends to appear side by side, underneath the plot with the variable names above the symbols, as they are in this blog post (the second plot). The opts function is now defunct, and theme does not appear to replicate its behaviour...

library("ggplot2")
ggplot(diamonds, aes(x = carat, y=price, shape = cut, group=interaction(cut, color), color=color)) +
geom_point() +
#opts(legend.direction = "horizontal", legend.position = "bottom")
#potential options, not all seem have an effect...
theme(legend.direction = "horizontal") +
theme(legend.position = "bottom") +
theme(legend.box = "vertical") +
theme(legend.title.align = 0)

...using my MS paint skills to illustrate the desired plot.

解决方案

Adapting from the previous suggestions with legend.box = "horizontal", I have found that you can get the legend titles on top using title.position = "top" in the guides for the scale_ functions. These have to be defined for each variable that makes up the legend else the title will be to the left.

ggplot(data = diamonds, 
       mapping = aes(x = carat, y = price, shape = cut,
                     group=interaction(cut, color), color=color)) +
  geom_point() +
  theme(legend.box = "horizontal",
        legend.position="bottom") +
  scale_shape(guide = guide_legend(title.position = "top")) +
  scale_colour_discrete(guide = guide_legend(title.position = "top", nrow = 1))

You could shift the titles to the center, as I suggested in the question, using title.hjust = 0.5. However, upon inspection, doing so might confuse the reader as to which colours/points refers to which variable.

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