R：删除所有不匹配的字符串矢量字母

Question

I have a string vector

d <- c("sladfj0923rn2", ääas230ß0sadfn", 823Höl32basdflk")

I want to remove all characters from this vector that do not match "az", "Az" and "'"

I tried to use gsub("![a-zA-z'], "", d) but that doesn't work.

Answer 1

We could even make your replacement pattern even tighter by doing a case insensitive sub :

d <- c("sladfj0923rn2", "ääas230ß0sadfn", "823Höl32basdflk")
gsub("[^a-z]", "", d, ignore.case=TRUE)

[1] "sladfjrn"  "assadfn"   "Hlbasdflk"

Answer 2

We can use the ^ inside the square brackets to match all characters except the one specified within the bracket

gsub("[^a-zA-Z]", "", d)
#[1] "sladfjrn"  "assadfn"   "Hlbasdflk"

data

d <- c("sladfj0923rn2", "ääas230ß0sadfn", "823Höl32basdflk")