bsxfun to multiply matrix with vector multiple times in for loop --> how faster?

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T 2017-3-6

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https://ww2.mathworks.cn/matlabcentral/answers/328380-bsxfun-to-multiply-matrix-with-vector-multiple-times-in-for-loop-how-faster

编辑： Matt J 2017-3-10

I have a 2D matrix of size NxN, and each row I am multiplying with a 1xN vector with bsxfun in a for loop like this:

for k=1:1000
   b(k)=mean(bsxfun(@times,tb_filter2d,d(k,:)),2);
  end

Is there a way to speed this up? d is of the size 1000xN.

Thank you!!

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James Tursa 2017-3-6

If tb_filter2d is your NxN matrix, how does this even work since the result of the RHS is a vector and you are assigning it to a scalar element location b(k)?

Rik 2017-3-6

Is there a reason you can't use something like meshgrid to remove the loop?

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回答（2 个）

Ankita Nargundkar 2017-3-9

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/328380-bsxfun-to-multiply-matrix-with-vector-multiple-times-in-for-loop-how-faster#answer_258073

1. If you are on MATLAB R2016b, you can use operators directly instead of bsxfun. Refer to this example

2. You can use repmat or reshape to optimize. Refer to this link

Something on similar lines, https://www.mathworks.com/matlabcentral/answers/210352-optimize-speed-up-a-big-and-slow-matrix-operation-with-addition-and-bsxfun