sampling from a matrix

Hello I am going to sample some columns in a matrix and return the columns that are not selected during the sampling. could you please help me?

Answer 1

[José-Luis]

bla = rand(10);
%Columns you sample:
my_cols = [1 5 7];
%Extract them:
sample = bla(:,my_cols);
nCols = 1:size(bla,2);
no_sample = nCols(~ismember(nCols,my_cols));
no_sample =bla(:,no_sample);

[Mohamad]

Dear Jose Thank you very much.

Answer 2

[dpb]

Sample how? If use randperm, say, as

icol=randperm(size(x,2),N);

to select N random columns from the array x to get the "nonsampled" columns you could instead simply use

inot=randperm(size(x,2),size(x,2)-N);

which is simply picking a random set of the obverse size to not sample--same thing in the end.

Or, if you are using the sampled column values first and then wanting the ones that weren't used both then first select as in the former and the other columns are simply

inot=setdiff([1:size(x,2)],icol);

[Mohamad]

hi dear dpd Thank you very much for the informative comments.