在ggplot2中包装图例文本

Question

在使用ggplot2生成图形的同时,我有一些很长的图例名称,我希望将它们包含在两行中.例如:

a <- (1:10)
b <- c(1,1.5,2,4,5,5.3,7,9,9.5,9.8)
places = c("Birmingham","Chester-le-street","Cambridge", "Newcastle-upon-Tyne","Peterborough","Cambridge", "Newcastle-upon-Tyne","Peterborough","Liverpool","Stratford-upon-Avon")
df1 = data.frame(a,b,places)
library(ggplot2)
i = ggplot(df1, aes(x=a, y=b)) + geom_point(aes(colour = places), size=3) + opts(legend.position="bottom")

当盒子设置在底部时,我该如何包装图例项目 - 比如2或3行？目前,传奇的七个项目彼此相邻.我希望它们显示在两行中(比如顶行的四个城镇和第二行的三个城镇).

提前谢谢了.

Answer 1

好的,鉴于您的编辑,您可能想要这样:

library(scales)
i + guides(colour = guide_legend(nrow = 2))

但是你可能会发现你仍然想要使用文本包装技术,以使它适合.

Answer 2

从你的例子:

df1$places<-sub("-", "- \n ", df1$places)  

i = ggplot(df1, aes(x=a, y=b)) + geom_point(aes(colour = places), size=3)

注意: - 您可以使用gsub将所有" - "替换为" - \n"

Answer 3

我发现非常方便的另一种包装图例标签的方法如下（所有归功于https://sites.google.com/site/simonthelwall/home/r/ggplot2#TOC-Wrapping-legend-labels）：

a <- (1:10)
b <- c(1,1.5,2,4,5,5.3,7,9,9.5,9.8)
places = c("Birmingham","Chester-le-street","Cambridge", "Newcastle-upon-Tyne","Peterborough","Cambridge", "Newcastle-upon-Tyne","Peterborough","Liverpool","Stratford-upon-Avon")
df1 = data.frame(a,b,places)
library(ggplot2)
i = ggplot(df1, aes(x=a, y=b)) + geom_point(aes(colour = places), size=3) 

i + scale_colour_discrete(labels = function(x) str_wrap(x, width = 5))