tha facet标签内的希腊符号

Question

我正在尝试使用ggplot2（v.2_2.2.1）facet_wrap创建一个绘图，我需要在一个facet标签中有一个希腊符号（五个中）。我试图在stackoverflow上使用这里发布的代码： example 1，example 2，example 3 但没有任何成功（getGrob不起作用，mf_labeller也是如此）。

任何人都可以帮助我吗？

以下是示例代码：

df <- data.frame(genes = rep(c("BA","MLL","pos","neg","PMLalpha+"),5), value = sample(1:100, 25, replace=TRUE))
df$genes <- factor(df$genes, levels = c("BA","MLL","pos","neg","PMLalpha+"), ordered = TRUE)
ggplot(df,aes(x=genes, y=value)) + geom_boxplot()+ 
  facet_wrap(~genes, ncol = 5,scales = "free_x")+
  scale_x_discrete(name="",
               breaks = c("BA","MLL","pos","neg","PMLalpha+"),
               labels = c("BA","MLL","pos","neg",expression(paste("PML", alpha,"+"))))

我可以重命名x轴刻度，但我不能在刻面标签中这样做。对不起，如果很明显，我会变得疯狂...... 谢谢你的建议和帮助！

Answer 1

这是一个使用labeller=label_parsed的技巧。

首先，为使用要解析的表达式的df$genes定义标签：

df$genes <- factor(df$genes, levels = c("BA","MLL","pos","neg","PMLalpha+"),
 ordered = TRUE, labels=c("BA","MLL","pos","neg",expression(paste("PML", alpha,"+"))))

然后在labeller=label_parsed中使用facet_wrap：

ggplot(df,aes(x=genes, y=value)) + geom_boxplot()+ 
  facet_wrap(~genes, ncol = 5, scales = "free_x", labeller = label_parsed)

正如您可以看到这与x轴标签混淆，但您可以在scale_x_discrete中修复它，如下所示：

ggplot(df,aes(x=genes, y=value)) + geom_boxplot()+ 
  facet_wrap(~genes, ncol = 5, scales = "free_x", labeller = label_parsed) +
  scale_x_discrete(name="",
               breaks = c("BA","MLL","pos","neg","paste(\"PML\", alpha, \"+\")"),
               labels = c("BA","MLL","pos","neg", expression(paste("PML", alpha,"+"))))