I have a dataframe where the variables are character-strings. How can I extract only those columns where at least one value matches a particular string? For example, in the dataframe below, I want a match of the string "AB", i.e. I want to subset out another dataframe containing the columns V1, V2 and V5.
V1 V2 V3 V4 V5
ABCD ABEF EFGJ AFASD JLKJLXKJ
LKJAF ROGIJ GREJWI SDFS ABKLJKJX
AFSD JLASDF JKLJ OIJPOI AFSD