從箱線與多層次

Question

我有一個箱形圖多層次D $ A + d $ b卸下空的水平

d = data.frame(value = c(1,2,3,100), a = c("A","A","B","A"), b = c("C","D","C","C")) 
boxplot(d$value ~ d$a + d$b, horizontal = TRUE) 

當您運行的代碼，你將看到BD組合仍顯示上升，但它是空的。我如何刪除它？

這只是一個玩具的例子。實際上，我有40多種組合，不想用手去除空白的組合。

Answer 1

你可以先（其drop參數一起）使用interaction來創建data.frame的新列，然後繪製它：

d <- data.frame(value = c(1,2,3,100), a = c("A","A","B","A"), b = c("C","D","C","C")) 
d <- within(d, interaction <- interaction(a, b, drop = TRUE)) 
boxplot(value ~ interaction, data = d, horizontal = TRUE)