如何在我的facet标签中插入希腊符号？

Question

如何在我的facet标签中插入希腊符号？

rggplot2labelfacet-wrap

3

我正在尝试使用ggplot2（v. 2_2.2.1）的facet_wrap创建一个图表，并且我需要在仅有的一个面板标签（共五个）中使用希腊符号。我曾经尝试过在Stack Overflow上发布的代码：

但是没有任何成功（getGrob无法工作，这也适用于mf_labeller）。

有人能帮帮我吗？

下面是示例代码：

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,"+"))))

我可以修改x轴刻度线的名称，但在分面标签中做不到。

- LenkaH

1个回答

网页内容由stack overflow 提供, 点击上面的

可以查看英文原文，
原文链接

- Djork · Accepted Answer

这里有一个技巧，使用labeller=label_parsed。首先，为df$genes定义标签，使用要解析的表达式：

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，这会导致x轴标签混乱，但可以通过以下方式在scale_x_discrete中进行修复:

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,"+"))))

编辑：针对后续问题的回答，以下是使用label_parsed解决多个变量的方法。包括所请求的空格在变量字符串中。

df$var2 <- c(rep(c('trt a','trt b'), NROW(df)/2),'trt a')
df$var2 <- factor(df$var2, levels=c('trt a','trt b'), ordered=T, labels=c(expression(paste("trt ", alpha)), expression(paste("trt ", beta))))

修复x轴：

ggplot(df,aes(x=var2, y=value)) + geom_boxplot() + facet_wrap(~var2, ncol = 5, scales = "free_x", labeller = label_parsed)

固定x轴：

ggplot(df,aes(x=var2, y=value)) + geom_boxplot() + 
  facet_wrap(~var2, ncol = 5, scales = "free_x", labeller = label_parsed) + 
  scale_x_discrete(name="",
                 breaks = c(expression(paste("trt ", alpha)), expression(paste("trt ", beta))),
                 labels = c(expression(paste("trt ", alpha)), expression(paste("trt ", beta))))