两个例子对我很有帮助.
我如何选择:1)名称以b或B开头的变量(即不区分大小写)或2)名称包含3的变量
df <- data.frame(a1 = factor(c("Hi", "Med", "Hi", "Low"),
levels = c("Low", "Med", "Hi"), ordered = TRUE),
a2 = c("A", "D", "A", "C"), a3 = c(8, 3, 9, 9),
b1 = c(1, 1, 1, 2), b2 = c( 5, 4, 3,2), b3 = c(3, 4, 3, 4),
B1 = c(3, 6, 4, 4))