difficulty filter file with big data

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AIRTON 2025-9-21

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https://ww2.mathworks.cn/matlabcentral/answers/2180097-difficulty-filter-file-with-big-data

评论： Walter Roberson 2025-9-22

filter_big_data.mat

在 MATLAB Online 中打开

I need of help me with this script. I want to filter all the columns but this is very slow.

there I have filtered only two columns.

My file loaded is only example.

clear all 
clc
tic
a = 1;
r = zeros(3268760,1); 
load ('filter_big_data'); % this file ís a matrix 576x3268760 double
for i = 1:2
    z1 = b(b(:,1) == 0, :); 
    s1 = sum(z1, 1);
    s2 = max(s1);
    r(a,1) = max(s1);
    a = a + 1;
end
toc

Elapsed time is 209.340817 seconds. % this time was elapsed for to filter two columns of

Thank by attention!!!

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AIRTON 2025-9-21

Hy Walter

you have reason!

I have changed my script.

Can you help me, I am inexperient with Matlab. I am learning.

Thanks!

Walter Roberson 2025-9-22

在 MATLAB Online 中打开

z1 = b(b(:,1) == 0, :);

That code does not depend on a or i so it is going to produce the same result for every iteration of the loop. Because of that, every iteration of the loop is going to perform the same operation.

I would suggest that the code should be closer to

tic
r = zeros(3268760,1); 
load ('filter_big_data'); % this file ís a matrix 576x3268760 double
for i = 1:2
    z1 = b(b(:,i) == 0, :); 
    s1 = sum(z1, 1);
    s2 = max(s1);
    r(i,1) = max(s1);
end
toc