MATLAB: Avoiding for loop with ismember

for loopismember

Hi, suppose N is a scalar, and c is a numerical vector with unique elements that are a subset of 1:N, i.e. its size is smaller or equal to N. For example, N=4, and c=[1 2 4]'; Then, is there a more elegant way to achieve this?
    cc = [];
for j = 1:N
    if ismember(j,c)
        cc      = [cc; N*(j-1)+c];
    end
end
Thanks!

Best Answer

[Fixed]
N = 15;
c = randperm(N,4);
c1  = sort(c(:));
cc = reshape(bsxfun(@plus,N*(c1 - 1),c1')',[],1);
or
oc =  ones(numel(c1),1);
cc = N*(kron(c1,oc) - 1) + kron(oc,c1);
or
c = c(:);
nn = numel(c);
cc = N*(repelem(c,nn) - 1) + repmat(c,nn,1);
Related Question