Subsetting Column from Matrix in R without specific column names specified

Question

I made a matrix a with character names "0", ..., "10". Now I make a subset list of column names, S. I want to subset the matrix a so that, I won't have the columns with names in S. I am trying to do the following but it's giving error. Any idea?

 > a
          0  1  2  3  4  5  6  7  8  9  10
     [1,] 1  1 11 21 31 41 51 61 71 81  91
     [2,] 1  2 12 22 32 42 52 62 72 82  92
     [3,] 1  3 13 23 33 43 53 63 73 83  93
     [4,] 1  4 14 24 34 44 54 64 74 84  94
     [5,] 1  5 15 25 35 45 55 65 75 85  95
     [6,] 1  6 16 26 36 46 56 66 76 86  96
     [7,] 1  7 17 27 37 47 57 67 77 87  97
     [8,] 1  8 18 28 38 48 58 68 78 88  98
     [9,] 1  9 19 29 39 49 59 69 79 89  99
    [10,] 1 10 20 30 40 50 60 70 80 90 100
    > colnames(a)
     [1] "0"  "1"  "2"  "3"  "4"  "5"  "6"  "7"  "8"  "9"  "10"

> S <- as.character(c(0,2))
> S
[1] "0" "2"
> a[,-S]
Error in -S : invalid argument to unary operator

Answer 1

You can try

a[,setdiff(colnames(a), S)]

Or

a[,!colnames(a) %in% S]