在ggplot2的条形图中为类别变量添加阴影替代区域

问题描述

我正在尝试使用ggplot2绘制条形图，如下所示:

I am trying t o plot a bar plot using ggplot2as follows:

library(ggplot2)
ggplot(mtcars, aes(factor(carb))) +
  geom_bar() +
  coord_flip()

x轴是连续变量，而y轴是绝对变量(factor).

x axis is a continous variable, while y axis is a categorical one (factor).

我想在每个条形后面添加备用阴影区域，以区分y轴上的因子.我知道我可以为此使用geom_rect().当它是factor时，如何计算该区域的y轴限制?矩形的x轴限制为-Inf至Inf.

I would like to add alternate shading area behind each bar to differentiate the factors in y axis. I know I can use geom_rect() for this. How to calculate the y axis limits for the area, when it is a factor? x axis limits for the rectangles would be -Inf to Inf.

我正在寻找与此图像相似的东西，但只寻找条形图而不是盒形图.

I am looking for something along the lines of this image, but for barplots instead of boxplots.

推荐答案

解决了

# Create data.frame with shading info
shading <- data.frame(min = seq(from = 0.5, to = max(as.numeric(as.factor(mtcars$carb))), by = 1),
           max = seq(from = 1.5, to = max(as.numeric(as.factor(mtcars$carb))) + 0.5, by = 1),
           col = c(0,1))

# Plot
ggplot() +
  geom_bar(data = mtcars, mapping = aes(factor(carb))) +
  geom_rect(data = shading,
            aes(xmin = min, xmax = max, ymin = -Inf, ymax = Inf,
                fill = factor(col), alpha = 0.1)) +
  scale_fill_manual(values = c("white", "gray53")) +
  geom_bar(data = mtcars, mapping = aes(factor(carb))) +
  coord_flip() +
  guides(fill = FALSE, alpha = FALSE)

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