Save Multiple Matrices from For Loop

Question

Michelle De Luna 2021-4-11

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/799182-save-multiple-matrices-from-for-loop

评论： Michelle De Luna 2021-4-14

Good afternoon!

I'm currently working on reading through various levels of a group of .nc files. Every time I read through the levels of an individual .nc file, I produce a 21x21 matrix representing the data values at 21 different latitudes and 21 different levels. Ideally, I would like to save each of my matrices from each of my .nc files separately so that I may then perform separate calculations on each of them. However, I am having trouble doing so. I've played around with my code for a couple of hours, but I can't seem to get it to work like I'd like it to. Any recommendations? Here's what I have so far...

Folder = 'C:\My\Folder\Here'
FileList = dir(fullfile(Folder, '*.nc'))
for iFile = 1:numel(FileList)
    file = fullfile(FileList(iFile).folder, FileList(iFile).name)
    latitude = ncread(file, 'lat');
    longitude = ncread(file, 'lon');
    time = ncread(file, 'time');
    level = ncread(file, 'lev')
    qv = []
    for i = 1:numel(level)
        i
        z = ncread(file, 'QV', [548, 130, i, 1], [1, 21, 1, 1])
        qv = [qv; z]                                                %this produces the 21x21 matrix...
    end
    qv(:,:,iFile) = qv                                              %this is where I am hoping to save each of my matrices separately..
end

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David Fletcher 2021-4-11

在 MATLAB Online 中打开

This seems to be a common problem tonight - is there a full moon? This line in the iFile loop

qv = []

is going to overwrite the location you are trying to store your matrices with nothing on every iteration

qv(:,:,iFile) = qv

So you read your data, put it into a store, go to the next iteration, overwrite your store with nothing, read your data, put it into the store, etc.

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Answer 1

Abhishek Gupta 2021-4-14

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https://ww2.mathworks.cn/matlabcentral/answers/799182-save-multiple-matrices-from-for-loop#answer_674696

在 MATLAB Online 中打开

Hi,

You can solve the issue as follows: -

Folder = 'C:\My\Folder\Here';
FileList = dir(fullfile(Folder, '*.nc'));
output = zeros(21,21,numel(FileList));  % initialize the 3D matrix to store 21x21 matrices
for iFile = 1:numel(FileList)
    file = fullfile(FileList(iFile).folder, FileList(iFile).name);
    latitude = ncread(file, 'lat');
    longitude = ncread(file, 'lon');
    time = ncread(file, 'time');
    level = ncread(file, 'lev');
    qv = [];
    for i = 1:numel(level)
        z = ncread(file, 'QV', [548, 130, i, 1], [1, 21, 1, 1]);
        qv = [qv; z];                                            %this produces the 21x21 matrix...
    end
    output(:,:,iFile) = qv;  % store 21x21 matrix                                                  
end