repeating a vector with increments

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Jeong Ho
Jeong Ho 2015-2-20
回答： arich82 2015-2-20
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

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回答（2 个）

Star Strider
Star Strider 2015-2-20
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
arich82
arich82 2015-2-20
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.

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