r - 刻度线标签中的数学表达式，ggplot2

Question

我想使用数学表达式制作刻度线标签。请参见下一个示例：

library(tidyverse)    
gl<-30
ggplot(data = data.frame(x = c(-5, 5)), aes(x)) +
      stat_function(fun = dt, args = list(df = 30))+ylab("f(t)")+
      geom_segment(aes(x=qt(.975,gl),xend=qt(.975,gl),y=0,yend=dt(qt(.975,gl),gl)))+
      scale_x_continuous("t", round(c(-5,qt(1-.975,gl),0,qt(.975,gl),5),3), limits=c(-5,5),labels=c("-5.000", "-2.042",  "0"  ,"list(q[0.95]==0.025)",  "5.000"))+
      annotate("segment", x = c(2.2), xend = c(3.8), 
               y = c(0.02), yend = c(.16), colour = "red", size=1, alpha=0.6, arrow=arrow())+
      annotate("segment", x = c(-1), xend = c(-3), 
               y = c(0.02), yend = c(.16), colour = 1, size=1, alpha=0.6, arrow=arrow())+
      stat_function(fun = dt, args = list(df = gl),
                    xlim = c(-5,qt(.975,gl)),
                    geom = "area",fill="red",alpha=0.5)+
        annotate("text", x = c(-3.8,3.8,4), y = c(0.18,0.18,.3), 
               label = c("1-alpha","alpha/2","list(q[0.95]==0.025)"),parse=T , size=4 , fontface="bold")+
      theme_bw()

如果线

scale_x_continuous("t", round(c(-5,qt(1-.975,gl),0,qt(.975,gl),5),3), limits=c(-5,5),labels=c("-5.000", "-2.042",  "0"  ,"list(q[0.95]==0.025)",  "5.000"))

被替换为

scale_x_continuous("t", round(c(-5,qt(1-.975,gl),0,qt(.975,gl),5),3), limits=c(-5,5),labels=c("-5.000", "-2.042",  "0"  ,"list(q[0.95]==0.025)",  "5.000"),parse=T)

得到一个错误：

scale_x_continuous("t", round(c(-5, qt(1 - 0.975, gl), 0, qt(0.975, ) 中的错误：未使用的参数 (parse = T)

如何在 scale_x_continuous 中实现数学表达式，就像在 annotate 中实现的那样？

标签： rggplot2axis-labels

Answer 1

xlabels <- c(
  ~ "-5.000",
  ~ "-2.042",
  ~ "0",
  ~ list(q[0.95]==0.025),
  ~ "5.000"
)
ggplot(......) + ...... + 
  scale_x_continuous("t", round(c(-5,qt(1-.975,gl),0,qt(.975,gl),5),3), 
                     limits=c(-5,5), 
                     labels= xlabels)