如何在我的一个构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 创建一个绘图，并且我只需要在一个方面标签中包含一个希腊符号(共五个).我曾尝试使用 Stack Overflow 上发布的代码:

• 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 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?

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

  Can anyone help me with that?

  Here is the example code:

  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,"+"))))
  

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

  解决方案

  Here is a trick that uses labeller=label_parsed.

  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,"+"))))
  

  Then use labeller=label_parsed in facet_wrap:

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

  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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