如何在一个方面标签中包含希腊符号? [英] How can I have a Greek symbol within one of my facet labels?

问题描述

我正在尝试使用ggplot2(v.2_2.2.1)facet_wrap创建图，并且我只需要在一个构面标签中使用希腊符号(五分之一).我尝试使用此处在堆栈溢出中发布的代码:

I'm trying to create a plot using ggplot2 (v. 2_2.2.1) facet_wrap, and I need to have a Greek symbol in only one facet label (out of five). I have tried to use code posted here on Stack Overflow:

• R希腊字母刻面网格中刻面标签的常用字母和普通字母
• 如何在facet_wrap中向标签添加表达式?

• R Greek letters and normal letters for facet label in R facet grid
• How to add expressions to labels in facet_wrap?
• How can I use grid to edit a ggplot2 object to add math expressions to facet labels?

但没有成功(getGrob无法正常工作，对于mf_labeller也是如此).

but without any success (getGrob is not working, and that's true also for the mf_labeller).

有人可以帮我吗?

这是示例代码:

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,"+"))))

我能够重命名x轴刻度线，但是我无法在构面标签中执行此操作.

I'm able to rename the x-axis tick, but I just can't do that within the facet labels.

推荐答案

以下是使用labeller=label_parsed的技巧.

首先，为使用解析的表达式的df$genes定义标签:

First, define labels for df$genes that uses the expression to be parsed:

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facet_wrap中使用labeller=label_parsed:

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

您可以看到它与x轴标签混淆了，但是您可以在scale_x_discrete中按如下所示对其进行修复:

As you can see this messes with the x-axis labels, but you can fix it in scale_x_discrete as follows:

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,"+"))))

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