Trying to optimise this loop

Question

James 2024-1-26

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2074931-trying-to-optimise-this-loop

评论： Shadow 2024-4-3

Hello,

I'm new to Matlab, and trying to write code that talks a 3-D array, and writes a csv file with the first two dimensions of one line, then repeated for each z entry. For instance an array of size 6,6,5 would output 36 values over 5 lines. The horrible code I wrote to do this is, how would I do this properly?

Thanks

James

  function WriteOutValuesToAFile(filename,M)
    fileID = fopen(filename,'w');
    for k=1:size(M,3);
      arr=M(:,1,k);
      fprintf(fileID, "%f",arr(1));
      for i=2:size(M,1);
fprintf(fileID,",%f",arr(i));    
      end
      
      for j=2:size(M,2);
	    arr=M(:,j,k);
	    for i=1:size(M,1);
           fprintf(fileID,",%f",arr(i));    
	    end
      end   
	  fprintf(fileID, "\n");
    end
    fclose(fileID);
  end

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Answer 1

Bruno Luong 2024-1-26

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https://ww2.mathworks.cn/matlabcentral/answers/2074931-trying-to-optimise-this-loop#answer_1398251

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function WriteOutValuesToAFile(filename,M)
fileID = fopen(filename,'wt');
for k=1:size(M,3);
    s = sprintf('%f,', M(:,:,k));
    s(end) = [];
    fprintf(fileID, "%s\n", s);
end
fclose(fileID);
end

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Answer 2

Shadow 2024-4-3

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2074931-trying-to-optimise-this-loop#answer_1435766

在 MATLAB Online 中打开

function WriteOutValuesToAFile(filename,M)
    text = "";
    for c = 1:size(M,3)
        text = text + mat2str(M(:,:,c)) + newline;
    end
    writelines(text,filename,Writemode="append",Encoding="UTF-8")
end