ggplot2：格式化图例类别

我希望能够做这样的事情：https://stackoverflow.com/a/30036603，除了使用“legend.text”而不是“axis.text.x”。这可能吗？

它会是这样的，除了它目前不工作（所有labs为斜体）：

data <- data.frame(labs = c("Oranges", "Apples", "Cucumbers"), counts = c(5, 10, 12))

ggplot(data = data) +
geom_bar(aes(x = labs, y = counts,fill=labs), stat="identity") +
theme(axis.text.x=element_text(face=ifelse(levels(data$labs)=="Cucumbers","plain","italic"))) +
  theme(legend.text=element_text(face=ifelse(levels(data$labs)=="Cucumbers","plain","italic")))

您可以调整比例来绘制可以包含斜体单词的表达式，而不是扰乱主题。例如

toexpr<-function(x) {
  getfun <- function(x) {
    ifelse(x=="Cucumbers", "plain", "italic")
  }
  as.expression(unname(Map(function(f,v) substitute(f(v), list(f=as.name(f), v=as.character(v))), getfun(x), x)))
}

ggplot(data = data) +
  geom_bar(aes(x = labs, y = counts,fill=labs), stat="identity") +
  scale_x_discrete(breaks =levels(data$labs), labels = toexpr(levels(data$labs))) +
  scale_fill_discrete(breaks=levels(data$labs), labels = toexpr(levels(data$labs))) + 
  theme(legend.text.align = 0)