如何将图例标题与ggplot2中图例框的中间对齐？

Question

我想将图例标题sex稍微移动到图例框的水平中心.我试过theme和guide_legend,但失败了.两种方式都不会改变图例标题的位置.

# example data from http://www.cookbook-r.com/Graphs/Legends_(ggplot2)/
df1 <- data.frame(
    sex = factor(c("Female","Female","Male","Male")),
    time = factor(c("Lunch","Dinner","Lunch","Dinner"), levels=c("Lunch","Dinner")),
    total_bill = c(13.53, 16.81, 16.24, 17.42)
)

library(ggplot2)
p <- ggplot(data=df1, aes(x=time, y=total_bill, group=sex, shape=sex, colour=sex)) +
    geom_line() + geom_point()

# no change
p + theme(legend.title = element_text(hjust = 0.5))
p + guides(color=guide_legend(title.hjust=0.5))

另外,我使用的是ggplot2_2.2.0.

Answer 1

你需要legend.title.align而不是legend.title:

p + theme(legend.title.align=0.5)