Replace substring with nothing

问题

How can I replace everything starting with the _ with just nothing?

Here is a simple data frame

d <- data.frame(a = c("A_foo1", "B_foo2", " _foo3"))

I want d to look like:

a
A
B
" "

回答1:

a <- c("A_foo1", "B_foo2", " _foo3")
gsub("_.*", "", a)
#[1] "A" "B" " "

来源：https://stackoverflow.com/questions/13570312/replace-substring-with-nothing