How can I calculate a weighted mean in Matlab?

Question

Jan-Erik 2013-2-18

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回答： Micke Malmström 2019-10-3

I have a 180-by-360 matrix of (surface temperature) values and I want to calculate a weighted average of all values given in this matrix. However, I need to weight these values with respect to latitude. Is there a way to calculate a weighted mean in Matlab? Please help me.

Thanks in advance for any help!

- Jan-Erik

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shelley 2015-10-20

Normally taking dim 1 mean of some, say 3x5 matrix A, can be seen as w=[1/3 1/3 1/3], and w*A returns you the answer.

Now if we want to take dim 1 weighted mean of A, we can set our weight in w = [1/6 2/3 1/6], then take w*A, which should return you a 1x5 row vector.

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Answer 1

Matt J 2013-2-18

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编辑：Matt J 2013-2-18

在 MATLAB Online 中打开

If A is your 180x360 matrix and W is a 180x1 vector of weights for the latitudes, do

weighted_mean = mean(W.'*A,2);

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Jason Garcia 2014-1-28

weighted_mean = mean(bsxfun(@times,A,w'),2)

Matt J 2014-1-28

在 MATLAB Online 中打开

weighted_mean = mean(bsxfun(@times,A,w'),2)

If that's what the OP intended, it would be more efficient to do

weighted_mean=w'.*mean(A,2);

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Answer 2

John Hock 2019-4-28

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Hi Everyone

I just want to ask one thing that if i have 2d array 2*4 and want to get weighted average with vector of 1*4

i want first row of A get multiplied with B and give weighted average as an output similarly for next row.

Please help

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Image Analyst 2019-4-28

在 MATLAB Online 中打开

Try

B = repmat(B, [2, 1]) % Make B 2*4
weightedMeans = sum(A.*B, 1); % Get weighted means within a row going across columns.

stelios loizidis 2019-5-27

在 MATLAB Online 中打开

Hello,

I have the following questuin: 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 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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