set.seed(42)
v1 <- sample(1:100,10)
v2 <- sample(LETTERS,10)
d <- data.frame(v1 = v1, v2 = v2)
d
#> v1 v2
#> 1 49 E
#> 2 65 N
#> 3 25 T
#> 4 74 R
#> 5 18 O
#> 6 100 C
#> 7 47 I
#> 8 24 D
#> 9 71 Z
#> 10 89 M
# subset data frame d to include only those rows whose first
# column does not include the values 49, 25 or 18
d[which(!d$v1 %in% c(49,25,18)),]
#> v1 v2
#> 2 65 N
#> 4 74 R
#> 6 100 C
#> 7 47 I
#> 8 24 D
#> 9 71 Z
#> 10 89 M
So basically I want to delete the columns 'Mssing', 'Do not understand the question, 'Cant choose', and 'Decline to answer' and all the responses to those options.