Mean and SD for 3D matrix

Hello,

I have a 3D matrix (140 rows, 572 columns) for 91 cases which are safed in one .mat file. How can I create a new .mat file with the average Matrix and one for the SD Matrix? I have tried:

FileData = load('Matrix.mat');

Matrix_Avg = mean(3, Parameter);

But always get an error.

Help is much appreciated!

[Rik]

From your other question I suspect you don't have a 3D array, but a struct array. Is that correct? Please attach your data or post code that creates similar data.

[doehr001]

Thank you for your reply! The data file is too big unfortunetly. The code is use in full is:

pfad = '/Users/...../';
liste = dir(fullfile(pfad,'*.xlsm'));
files = {liste.name};
xlRange = 'A2:UZ141'
for i=1:numel(files)
    thisSheet = sprintf('Sheet1');
    fullFileName = fullfile(pfad,files{i})
    if exist(fullFileName, 'file')
        % Variable name
        Parameter{i} = xlsread (fullFileName, thisSheet, xlRange);
    else
        message = sprintf('File not found:\n%s', fullFileName);
        uiwait(warndlg(message));
    end
end
 
Matrix = cat(3,Parameter{:});
save( 'Matrix.mat', 'Matrix')
Matrix_Avg = mean(3, Matrix);
Matrix_SD   = std(3,Matrix);
save('Matrix_Avg.mat', 'Matrix_Avg')
save('Matrix_SD.mat', 'Matrix_SD')

Answer 1

[Steven Lord]

The cat function is one of the few (if not the only) functions where the dimension input comes first. In most other functions (including both mean and std) it comes after the data.

A = randi(16, 4, 4);
B = magic(4);
C = cat(3, A, B) % Concatenate in dimension 3

C = 
C(:,:,1) =

     4     4    14     9
    13     6     9    15
    12     8     5     6
     6    13    11     6


C(:,:,2) =

    16     2     3    13
     5    11    10     8
     9     7     6    12
     4    14    15     1

D = mean(C, 3) % Take the mean along dimension 3

D = 4×4

10.0000 3.0000 8.5000 11.0000 9.0000 8.5000 9.5000 11.5000 10.5000 7.5000 5.5000 9.0000 5.0000 13.5000 13.0000 3.5000

[doehr001]

Thank you Steven! When I use the:

Avg = mean(3, Matrix);

I always get an error. Now I am not clear why as there is no explanation other than error in line ...

The matrix I am loading is 140x572/ 91 doubles. Do you have any idea why I am getting this error?

[Rik]

Did you read what Steven wrote? The syntax for the mean function is not what you wrote, it should be mean(data,dim).

[doehr001]

Yes, I did. I changed it to Avg = mean(Matrix, 3);

I still get the error.

[Steven Lord]

What is the full and exact text (everything displayed in red and/or orange) of the error/warning messages you received when you ran the following code?

Avg = mean(Matrix, 3);

[doehr001]

The error is:

Error in XLSRead_MatrixExport_Feb2021 (line 33)

MAvg = mean(Matrix, 3);

I have exported a view of the files so that I can upload a sample .mat file.

[Rik]

When posting an error message, please make sure to post all the red text. And please use the layout tools to format your code as code.