R语言ggplot自定义绘图函数：如何将字符串作为变量名传递？

你推测的问题点完全正确：问题出在data.frame(VarName = VectorToGraph)和aes(x = VarName)这两处。前者是把数据框的列名固定成了"VarName"，而非你传入的VarName参数的字符串值；后者是直接引用这个硬编码的列名，导致X轴显示固定文本。

下面提供两种简洁的修改方案：

方案一：先创建临时列再重命名 #

DistribGraph <- function(VectorToGraph, VarName = "var", title,
                         limit_lo = 50, limit_hi = 150, bin_width = 5, tik_width = 10) {
  
  data <- data.frame(temp_col = VectorToGraph)
  colnames(data) <- VarName  # 将列名替换为传入的字符串参数
  
  graph <- ggplot(data) +
    aes(x = .data[[VarName]]) +  # 动态引用对应列名
    ggtitle(title) + 
    scale_x_continuous(breaks = seq(limit_lo, limit_hi, tik_width), 
                       limits = c(limit_lo, limit_hi)) +
    geom_histogram(aes(y = after_stat(density)),
                   binwidth = bin_width, 
                   fill = "#69b3a2", 
                   boundary = limit_lo,
                   color = "#e9ecef",  
                   alpha = 0.9) +
    theme(plot.title = element_text(size = 10, face = "bold")) +  
    stat_function(fun = dnorm, args = list(mean = mean(VectorToGraph), 
                                           sd = sd(VectorToGraph)))
  
  return(graph)
}

方案二：直接动态命名数据框列 #

用setNames一步完成数据框创建与列名设置，代码更紧凑：

DistribGraph <- function(VectorToGraph, VarName = "var", title,
                         limit_lo = 50, limit_hi = 150, bin_width = 5, tik_width = 10) {
  
  data <- setNames(data.frame(VectorToGraph), VarName)  # 直接将列名设为传入的字符串
  
  graph <- ggplot(data) +
    aes(x = .data[[VarName]]) +
    ggtitle(title) + 
    scale_x_continuous(breaks = seq(limit_lo, limit_hi, tik_width), 
                       limits = c(limit_lo, limit_hi)) +
    geom_histogram(aes(y = after_stat(density)),
                   binwidth = bin_width, 
                   fill = "#69b3a2", 
                   boundary = limit_lo,
                   color = "#e9ecef",  
                   alpha = 0.9) +
    theme(plot.title = element_text(size = 10, face = "bold")) +  
    stat_function(fun = dnorm, args = list(mean = mean(VectorToGraph), 
                                           sd = sd(VectorToGraph)))
  
  return(graph)
}

关键说明 #

使用.data[[VarName]]是ggplot官方推荐的动态引用列的方式，能避免非标准求值带来的变量识别问题。修改后调用原示例代码，X轴就会正确显示传入的"mpg"字符串。

内容的提问来源于stack exchange，提问作者BoTz