在帶有刻面（R，ggplot2）的箱圖中繪制備用矩形

Question

我正在使用以下代碼。

 mtcars2 <- mtcars
 library(ggplot2)
 mtcars2$carb <- as.factor(mtcars2$carb)
 mtcars2$am <- as.factor(mtcars2$am)
 sort_table <- data.frame("carb" = c(1,2,3,4,6,8), 
     "class" = c("class A", "class B", "class A", "class C", "class B", "class A"))
 odd_numbers <- seq(1,6,2)
 mtcars2 <- merge(mtcars2, sort_table, by = "carb")
 ggplot(mtcars2) + 
     geom_rect(data = mtcars2[odd_numbers, ], xmin = odd_numbers - 0.5, xmax = odd_numbers + 
     0.5, ymin = -Inf, ymax = Inf, fill = 'grey', alpha = 0.5) + 
     geom_boxplot(aes(x = carb, y = mpg, fill = am), position = position_dodge(0.9))

這樣可以很好地產生帶有交替陰影的箱形圖。

現在，我想為每個類添加構面，因此我使用以下代碼。

 ggplot(mtcars2) + 
     geom_rect(data = mtcars2[odd_numbers, ], xmin = odd_numbers - 0.5, xmax = odd_numbers + 
     0.5, ymin = -Inf, ymax = Inf, fill = 'grey', alpha = 0.5) + 
     geom_boxplot(aes(x = carb, y = mpg, fill = am), position = position_dodge(0.9)) + 
     facet_grid(cols = vars(class), scales = "free_x", switch = "x", space = "free") + 
     theme(panel.spacing.x = unit(0, "pt"), strip.background = element_rect(
         color="black", size=0.5, linetype="solid"))

這將產生以下箱線圖。

不幸的是，陰影現在僅應用於第一個構面。 如何在整個圖上對每個面應用連續陰影，以便在carb = 6后還有另一個矩形？ 謝謝。

Answer 1

事物將根據您提供的data.frame中存在的facet變量顯示適當的facet。 提供適當的data.frame，並進行適當的映射，例如：

df_tile <- data.frame(carb = c(1, 8, 6), class = c('class A', 'class A', 'class B'))

ggplot(mtcars) + 
    geom_tile(aes(x = factor(carb), y = 1, height = Inf, width = 1), data = df_tile, alpha = 0.3) + 
    geom_boxplot(aes(x = carb, y = mpg, fill = am), position = position_dodge(0.9)) + 
    facet_grid(cols = vars(class), scales = "free_x", space = "free") + 
    theme(panel.spacing.x = unit(0, "pt"), strip.background = element_rect(
        color="black", size=0.5, linetype="solid"))