如何使用plotmath更新ggplot图例标签

Question

我正在尝试更新ggplot图例标签以使用plotmath，但是，当我这样做时，它会将先前合并的图例分成两部分。举个例子可能更容易理解：

# test data and the default plot gives the correct colours and linetypes 
# in the legend but the labels are not parsed (as have not tried to yet!)

test = data.frame(x = 1:10, y = 1:10, grp=factor(rep(c("g1", "g2"),each=5)))

ggplot(test, aes(y=y, x=x, linetype=grp, colour=grp)) +
  geom_line()  

我想要的是在上面的图中保留图例键，但更改图例标签。我尝试了下面的方法，它们现在解析plotmath，但分离了图例键。

ggplot(test, aes(y=y, x=x, linetype=grp, colour=grp)) +
  geom_line() + 
  scale_linetype_discrete(breaks=c("g1", "g2"), labels = parse(text=c("g[1]", "g[2]"))) +
  scale_colour_discrete(breaks=c("g1", "g2"), labels = parse(text=c("g[1]", "g[2]"))) 


# same as before
ggplot(test, aes(y=y, x=x, linetype=grp, colour=grp)) +
  geom_line() + 
  scale_linetype_manual(values=1:2, breaks=c("g1", "g2"), labels = parse(text=c("g[1]", "g[2]"))) +
  scale_colour_manual(values=1:2, breaks=c("g1", "g2"), labels = parse(text=c("g[1]", "g[2]"))) 

我如何才能保留基本绘图的密钥，同时使用plotmath更新标签(而不更改原始数据)？

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Answer 1

这与labels = c(~g[1],~g[2])一起工作

ggplot(test, aes(y=y, x=x, linetype=grp, colour=grp)) +
  geom_line() + 
  scale_linetype_discrete(breaks=c("g1", "g2"), 
                          labels = c(~g[1],~g[2])) + 
  scale_colour_discrete(breaks=c("g1", "g2"),
                        labels = c(~g[1],~g[2]))