r - How to select specific columns containing certain strings/characters? -

i have dataframe:

df1 <- data.frame(a = c("correct", "wrong", "wrong", "correct"),   b = c(1, 2, 3, 4),   c = c("wrong", "wrong", "wrong", "wrong"),   d = c(2, 2, 3, 4))        b c     d correct 1 wrong 2 wrong   2 wrong 2 wrong   3 wrong 3 correct 4 wrong 4 

and select columns either strings 'correct' or 'wrong' (i.e., columns b , d in df1), such dataframe:

df2 <- data.frame(a = c("correct", "wrong", "wrong", "correct"),         c = c("wrong", "wrong", "wrong", "wrong"))              c 1 correct wrong 2   wrong wrong 3   wrong wrong 4 correct wrong 

can use dplyr this? if not, function(s) can use this? example i've given straightforward, in can (dplyr):

select(df1, a, c) 

however, in actual dataframe, have 700 variables/columns , few hundred columns contain strings 'correct' or 'wrong' , don't know variable/column names.

any suggestions how quickly? lot!

you can use base r filter operate on each of df1's columns , keep ones satisfying logical test in function:

filter(function(u) any(c('wrong','correct') %in% u), df1) #            c #1 correct wrong #2   wrong wrong #3   wrong wrong #4 correct wrong 

you can use grepl:

filter(function(u) any(grepl('wrong|correct',u)), df1)