分面 (facetwrap(), facetgrid()) R facetwrap(facets, nrow = NULL, ncol = NULL, scales = "fixed", shrink = TRUE, as.table = TRUE, switch = NULL, drop = TRUE, dir = "h", strip.position = "top") R library(ggplot2) 使用内置的 iris 数据集 data(iris) 按照 Species 变量进行分面 ggplot(iris, aes(x = Sepal.Length, y = Sepal.