repeating a vector with increments

Dear Matlab Central users, Hi, I have a row vector I and I want to create a row vector [I I+n I+2*n ... I+(N-1)*n] where N>1 and n are positive integers. For example, if I = [2 3] and N = n = 3, [2 3 5 6 6 9] Is there a trick to doing this efficiently? Thank you all!

Best, John

Answer 1

[Star Strider]

The output vector you listed does not seem to me to correspond to the rule for it you posted. Please clarify.

This otherwise seems to work:

N = 3;
I = [2 3];
Q = (cumsum(ones(N,2))-1)*N;
Ym = bsxfun(@plus, I, Q);
Yv = reshape(Ym', 1, []);       % Output

produces:

Yv =

       2     3     5     6     8     9

Answer 2

[arich82]

Assuming you have a typo in your example and your desired output is actually

[2, 3, 5, 8, 9]

(i.e. an 8 instead of the repeated 6), then I think this should do what you want:

n = 3; 
N = 3;
a = [2, 3];
b = n*[0:N-1];
c = bsxfun(@plus, a.', b);
c = c(:).'

or as a messy one-liner:

reshape(bsxfun(@plus, [2, 3].', 3*(0:3-1)), 1, []);

No gurantees that someone won't have a more clever solution, but if this doesn't give the desired result, perhaps a little more clarification would be helpful.