I have a matrix, like the one generated with this code:
> m = matrix(data=c(1:50), nrow= 10, ncol = 5);
> colnames(m) = letters[1:5];
If I filter the columns, and the result have more than one column, the new matrix keeps the names. For example:
> m[, colnames(m) != "a"];
b c d e
[1,] 11 21 31 41
[2,] 12 22 32 42
[3,] 13 23 33 43
[4,] 14 24 34 44
[5,] 15 25 35 45
[6,] 16 26 36 46
[7,] 17 27 37 47
[8,] 18 28 38 48
[9,] 19 29 39 49
[10,] 20 30 40 50
Notice that here, the class is still matrix:
> class(m[, colnames(m) != "a"]);
[1] "matrix"
But, when the filter lets only one column, the result is a vector, (integer vector in this case) and the column name, is lost.
> m[, colnames(m) == "a"]
[1] 1 2 3 4 5 6 7 8 9 10
> class(m[, colnames(m) == "a"]);
[1] "integer"
The name of the column is very important.
I would like to keep both, matrix structure (a one column matrix) and the column's name.
But, the column's name is more important.
I already know how to solve this by the long way (by keeping track of every case). I'm wondering if there is an elegant, enlightening solution.
