在 ggplot2 字幕的 plotmath 表达式中包含条件元素

Question

我正在尝试编写一个自定义函数，我想在 ggplot2 绘图字幕中显示效果大小估计及其置信区间。我正在使用plotmath 正确显示希腊字母和其他数学符号。

这就是我想要的两种字幕的样子-

为了实现这一点，我编写了一个简单的函数——

# set up
set.seed(123)
library(tidyverse)
library(cowplot)

# creating a fictional dataframe with effect size estimate and its confidence
# intervals
effsize_df <- tibble::tribble(
  ~estimate, ~conf.low, ~conf.high,
  0.25, 0.10, 0.40
)

# function to prepare subtitle
subtitle_maker <- function(effsize_df, effsize.type) {
  if (effsize.type == "p_eta") {
    # preparing the subtitle
    subtitle <-
      # extracting the elements of the statistical object
      base::substitute(
        expr =
          paste(
            eta["p"]^2,
            " = ",
            effsize,
            ", 95% CI",
            " [",
            LL,
            ", ",
            UL,
            "]",
          ),
        env = base::list(
          effsize = effsize_df$estimate[1],
          LL = effsize_df$conf.low[1],
          UL = effsize_df$conf.high[1]
        )
      )
  } else if (effsize.type == "p_omega") {
    # preparing the subtitle
    subtitle <-
      # extracting the elements of the statistical object
      base::substitute(
        expr =
          paste(
            omega["p"]^2,
            " = ",
            effsize,
            ", 95% CI",
            " [",
            LL,
            ", ",
            UL,
            "]",
          ),
        env = base::list(
          effsize = effsize_df$estimate[1],
          LL = effsize_df$conf.low[1],
          UL = effsize_df$conf.high[1]
        )
      )
  }

  # return the subtitle
  return(subtitle)
}

请注意，条件语句的代码只有一行不同：eta["p"]^2（如果是"p_eta"）或omega["p"]^2（如果是"p_omega"），其余代码相同。我想重构这段代码以避免这种重复。

我不能有条件地将eta["p"]^2 和omega["p"]^2 分配给函数体中的不同对象（比如说effsize.text <- eta["p"]^2），因为R 会抱怨找不到对象eta 和omega在环境中。

我该怎么做？

---------- 后记---------- ----------------

以下是用于创建上面显示的组合图的代码-

# creating and joining two plots (plot is shown above)
cowplot::plot_grid(
  # plot 1
  ggplot(mtcars, aes(x = wt, y = mpg)) + geom_blank() +
    labs(
      subtitle = subtitle_maker(effsize_df, "p_omega"),
      title = "partial omega"
    ),
  # plot 2
  ggplot(mtcars, aes(x = wt, y = mpg)) + geom_blank() +
    labs(
      subtitle = subtitle_maker(effsize_df, "p_eta"),
      title = "partial eta"
    ),
  labels = c("(a)", "(b)"),
  nrow = 1
)

Answer 1

quote 和 bquote 的组合会有所帮助，

subtitle_maker <- function(d, type){

  et <- if(type == 'a') quote(eta) else if(type == 'b') quote(omega)

  bquote(.(et)['p']^2==.(d$x)~", 95% CI ["*.(d$y)*","*.(d$z)*"]")

}

d <- list(x=1,y=2,z=3)
grid::grid.newpage()
grid::grid.text(subtitle_maker(d,"a"), y=0.3)
grid::grid.text(subtitle_maker(d,"b"), y=0.7)

注意：或替换而不是bquote，这只是个人喜好

subtitle_maker <- function(effsize_df, effsize.type) {

  effsize.text <- if (effsize.type == "p_eta") quote(eta["p"]) else 
    if (effsize.type == "p_omega") quote(omega["p"])

      base::substitute(
        expr =
          paste(effsize.text^2,
            " = ",
            effsize,
            ", 95% CI",
            " [",
            LL,
            ", ",
            UL,
            "]",
          ),
        env = base::list(effsize.text = effsize.text,
          effsize = effsize_df$estimate[1],
          LL = effsize_df$conf.low[1],
          UL = effsize_df$conf.high[1]
        )
      )
}

Answer 2

这是一个 unicode 解决方案。我使用 dplyr 中的 case_when 让生活更轻松。

# function to prepare subtitle
subtitle_maker <- function(effsize_df, effsize.type) {
  # preparing the subtitle
  subtitle <-
    # extracting the elements of the statistical object
    base::substitute(
      expr =
        paste(
          effsize_sym["p"]^2,
          " = ",
          effsize,
          ", 95% CI",
          " [",
          LL,
          ", ",
          UL,
          "]",
        ),
      env = base::list(
        effsize = effsize_df$estimate[1],
        LL = effsize_df$conf.low[1],
        UL = effsize_df$conf.high[1],
        effsize_sym = case_when(
          effsize.type == "p_eta" ~ "\U1D702",
          effsize.type == "p_omega" ~ "\U1D714",
          TRUE ~ NA_character_
        )
      )
    )

  # return the subtitle
  return(subtitle)
}