Dear all,
I would like to ask whether anyone has experience with the problem below.
I want to select a subset of the sample (see data below) so that each level
(1,2,3,4 in the example) for every variable (v1,v2,v3,v4 in the example) is
shown at least once in the subset. I also want the sample size of the
subset to be as small as possible. Any help on it is greatly appreciated.
Id v1 v2 v3 v4
[1,] 1 1 2 4 3
[2,] 2 2 1 3 4
[3,] 3 4 2 4 2
[4,] 4 1 1 2 3
[5,] 5 3 2 3 4
[6,] 6 3 1 1 1
[7,] 7 3 4 3 1
[8,] 8 4 4 4 4
[9,] 9 1 2 2 1
[10,] 10 4 1 1 2
[11,] 11 2 4 3 2
[12,] 12 1 4 2 3
[13,] 13 2 3 3 4
[14,] 14 4 3 1 2
[15,] 15 3 2 1 2
[16,] 16 2 3 2 3
[17,] 17 1 4 1 4
[18,] 18 2 3 4 3
[19,] 19 4 1 4 1
[20,] 20 3 3 2 1
Thanks,
Peter
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