Skipping files in a set

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MR0d 2019-11-27

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https://ww2.mathworks.cn/matlabcentral/answers/493566-skipping-files-in-a-set

评论： MR0d 2019-12-2

I have 600 .vec files from a recent experiment and I need to remove/skip certain files from this group because they contain bad data. Say I need to remove files 132, 290, and 404. How would I do this? Here is the code I have for creating the matrices I need. Thank you.

rightfiles=dir('*.vec'); % Selects only the files in the directory ending with .vec. Generates a 600x1 struct.
for z=1:1:size(rightfiles)
    f=importdata([rightfiles(z).name]);%Transitions data from .vec to .mat
    %Sets x,y,u,v into matrices of only columns 1-4 from rightfiles, respectively
    x=f.data(:,1);
    y=f.data(:,2);
    u=f.data(:,3);
    v=f.data(:,4);
    
    %Reshapes x,y,u,v into IxJ matrices
    xx=reshape(x,[I,J])';
    yy=reshape(y,[I,J])';
    uu=reshape(u,[I,J])';
    vv=reshape(v,[I,J])';
    
    %Convert to the correct units
    ConversionU=uu.*(m_pix/dt);
    ConversionV=vv.*(m_pix/dt);
    ConversionX=xx*m_pix;
    ConversionY=yy*m_pix;
    
    %Stack the vec files
    U(:,:,z)=ConversionU;
    V(:,:,z)=ConversionV;
    X(:,:,z)=ConversionX;
    Y(:,:,z)=ConversionY;
end

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KSSV 2019-11-28

How you will decide the files have bad data?

MR0d 2019-12-2

I have already gone through the data and selected the files with bad data.

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Answer 1

Jan 2019-11-28

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https://ww2.mathworks.cn/matlabcentral/answers/493566-skipping-files-in-a-set#answer_403793

编辑：Jan 2019-11-28

在 MATLAB Online 中打开

What does "files 132, 290, and 404" mean? Are these the indices in rightfiles, or are these parts of the file name?

rightfiles=dir('*.vec');
rightfiles([132, 290, 404]) = [];
for z = 1:numel(rightfiles)
    f = importdata(rightfiles(z).name);
    ...

I've added some changes:

size(rightfield) replies a vector. 1:1:vector might reply something other than you expect. Although this works here for accident, it is safer to use numel instead.
1:x looks nicer than 1:1:x
No need for square brackets around rightfiles(z).name. The [ and ] are the operator for concatenation. With one input only, there is nothing to concatenate.

Apply a pre-allocation before the loop. Letting arrays grow iteratively is extremely expensive.

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MR0d 2019-12-2

The random numberes I selected were just examples. They are random indices of rightfiles that I would like to exclude. Thank you for the advice. And I do have lines for pre-allocation, just didn't think it was important for my question so I did not include them. Thank you very much.

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Answer 2

Image Analyst 2019-11-28

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https://ww2.mathworks.cn/matlabcentral/answers/493566-skipping-files-in-a-set#answer_403813

在 MATLAB Online 中打开

Make a function calls HasGoodData() that take in f and determines if the data is bad or not and returns true for good data and false for bad data. Then, in your loop...

for z = 1 : size(rightfiles)
    f=importdata([rightfiles(z).name]); % Transitions data from .vec to .mat
    if ~HasGoodData(f)  % If not good data...
        continue; % Skip this file by jumping to the very bottom of the loop but continuing with the next iteration.
    end
    % Run code for good data...
end % of for loop