Execute code faster for saving files with a matrix

Question

Adrian Verdin 2019-7-9

0
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https://ww2.mathworks.cn/matlabcentral/answers/470793-execute-code-faster-for-saving-files-with-a-matrix

回答： Stephen23 2019-7-9

Hey guys! How are you. I need my code to execute faster. Here's the deal.

I have a matrix which is: datos2009(141214 x 11). I need to save files extracting information from that matrix, in the first column I have to save the data from 8, then the 10 and so on.

datos2009=[

8 29.24 5.96 10.6 0.06 0.69 22 72 -95.16 18.11 42.1

8 29.32 5.93 10.6 0.08 0.9 8 14 -95.16 18.11 42.1

8 30.19 6 10.6 0.06 0.69 14 28 -95.16 18.11 42.03

10 51.76 6.06 10.3 0.05 0.59 27 83 -95.16 18.11 41.42

10 51.84 5.66 10.3 0.05 0.59 14 40 -95.16 18.11 41.42

11 55.33 5.6 10.3 0.05 0.59 19 40 -95.16 18.11 41.37

11 55.68 5.9 10.3 0.07 0.8 15 39 -95.16 18.11 41.37]

prompt = 'Indique la ruta para guardar los archivos';
fpath=input(prompt,'s');
j=0;
k=datos2009(1);
header={'Costura', 'Kilometraje', 'Posición horaria', 'Espesor', 'Porcentaje de profundidad', 'Profundidad', 'Largo','Ancho', 'Longitud GPS', 'Latitud GPS', 'Elevación'};
cont=1;
values2009=zeros(50,11);
for i=1:size(datos2009)
    j=datos2009(i);
    if j==k
        
        values2009(cont,:)=datos2009(i,:);
        cont=cont+1;
    else
        zeroRow=~all(values2009, 2);
        values2009(zeroRow,:)=[];
        
        d = [header;num2cell(values2009)];
        fileName=sprintf(strcat('File','%04d','_T_%d.csv'),k,k);
        fullFileName=fullfile(fpath,fileName);
        xlswrite(fullFileName,d);
        values2009=zeros(50,11);
        cont=1;
        values2009(cont,:)=datos2009(i,:);
        cont=cont+1;
        k=j;
    end
end

Any ideas how to run faster my code, taking into consideration that it takes around 12 hours to finish the job, about 5000 files are saved.

Thanks in advance.

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Stephen23 2019-7-9

编辑：Stephen23 2019-7-9

"Any ideas how to run faster my code"

Don't use xlswrite to write text files!

Do not convert between data classes (e.g. split numeric matrix into cell array).

If speed is your main concern, then write to file using low-level commands, e.g. fprintf.

Adrian Verdin 2019-7-9

Stephen Cobeldick thank you so much, it worked what you suggested (It just took 8 minutes instead of 14 hours), I ask you if you can move your comment to an answer in order to give you the credit.

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