Mean of mutiple variables

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ali akbar 2020-12-11

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https://ww2.mathworks.cn/matlabcentral/answers/690900-mean-of-mutiple-variables

评论： dpb 2020-12-11

I have 5 '.mat' data files where each datafile contains 1 by 19 cell (each cell size = 512 by 9). I wanted to find the mean of the 4th column of 1st cell from all 5 data files.

Here is a look at the code.

 load('data1a.mat');load('data2.mat');load('data3.mat');load('data4.mat');load('data5.mat');...
% Extracting the 4th column
a=data1a{1,1}(:,4);b=data2{1,1}(:,4) and so on...
    m=(a+b+c+d+e)/5

Now people in stoneage might used to do this kind of laborious exercise. I am wondering if anyone could give a one/two liner answer for finding mean which is not naive like mine.

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Stephen23 2020-12-11

在 MATLAB Online 中打开

Copy and pasting code like this is a sign that you are doing something wrong:

load('data1a.mat');load('data2.mat');load('data3.mat');load('data4.mat');load('data5.mat');...

Learn to use arrays and indexing! For example:

https://www.mathworks.com/help/matlab/import_export/process-a-sequence-of-files.html

ali akbar 2020-12-11

data1a.mat

please see attached.

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Answer 1

dpb 2020-12-11

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https://ww2.mathworks.cn/matlabcentral/answers/690900-mean-of-mutiple-variables#answer_572465

编辑：dpb 2020-12-11

在 MATLAB Online 中打开

d=dir('data*.mat');        % or similar list. Name files so can use appropriate wildcard expression
total=0;
for i=1:numel(d)
  data=load d(i).name;
  total=total+structfun(@(x)sum(x{1}(:,4)),data);
end
mn=mean(total);

Above does the summation; same result if were to use mean in the anonymous function as well if same number elements in each cell array.

If the variables were named consistently would be easier to code; above handles whatever they are inside the .mat files as long as just one variable per file.