Calculate weighted average of a 2D matrix

Question

Abdul Wahab 2018-8-7

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https://ww2.mathworks.cn/matlabcentral/answers/413975-calculate-weighted-average-of-a-2d-matrix

评论： stelios loizidis 2019-5-23

Dear all, I hope all is well. I am working with a 2D Matrix that is 376x481. I would like to calculate the weighted average of this matrix for each row, such that the desired output should be sized 376 X 1. I would greatly appreciate any help with this problem.

Thanks.

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Answer 1

James Tursa 2018-8-7

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https://ww2.mathworks.cn/matlabcentral/answers/413975-calculate-weighted-average-of-a-2d-matrix#answer_331960

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E.g.,

w = 1x481 vector of weights
M = your 376x481 matrix of values
result = sum(M.*w,2) / sum(w);

or

sum(bsxfun(@times,M,w),2) / sum(w);

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James Tursa 2018-8-8

Can you provide us with some info on what data this matrix contains and how it was generated? Then maybe we can make a stab at what you might want to do for weights.

Abdul Wahab 2018-8-8

This matrix is populated with a non-dimensional variable (376 rows) and associated time history of 481 hours. So each row is then a representation of how this non-dimensional variable is changing through 481 hours (one column for every hour). This non-dimensional number varies in a specific order where it contains both unique and non-unique values of this non-dimensional variable. I would like to figure out the weight vector of the non-unique and unique values in every row and get the weighted average instead of a simple mean. I hope this provides some more insight into my problem.

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Answer 2

Thorsten 2018-8-8

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https://ww2.mathworks.cn/matlabcentral/answers/413975-calculate-weighted-average-of-a-2d-matrix#answer_331961

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X = rand(376, 481);
w = rand(1, size(X, 2));
Xw = bsxfun(@times, X, w);
m = mean(Xw, 2);

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stelios loizidis 2019-5-23

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Hello,

I saw the commands you wrote above and I have the following question; I have a matrix e.g

For this matrix I have to make a weighted average for each row. That is [5+3+(4/5)*(3+1)] / 4 =16/5. Also, if there is only one number and the rest zero (row 3) the weighted average should be [5+0+0+0]/ 1 =5 and the end we choose the largest weight average. How does this work?

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