regex - Trim part of a string in dataframe

Question

If I have a dataframe structure like that:

AA1_123.zip
BB2_456.txt
CCC_789.doc

How can I change it to this:

AA1
BB2
CCC

Answer 1

You could try sub

sub('_.*', '', df1$Col)
#[1] "AA1" "BB2" "CCC"

data

df1 <- structure(list(Col = c("AA1_123.zip", "BB2_456.txt", 
"CCC_789.doc"
)), .Names = "Col", class = "data.frame", row.names = c(NA, -3L))