从具有多个级别的箱形图中删除空级别

Question

我有一个多层次的箱形图 d$a + d$b

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)

当您运行该代码时，您会看到 B.D 组合仍然显示，但它是空的。如何删除它？

这只是一个玩具示例。实际上，我有 40 多种组合，不想手动删除空白组合。

Answer 1

您可以先使用interaction(连同其drop 参数)创建一个新的data.frame 列，然后绘制它:

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)