# Can anyone help me figure out the preallocation of the unknown matrix which no. of rows changing in every cycle? Thank in advance

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SA on 23 Feb 2021
Commented: SA on 23 Feb 2021
close all; clc;
tic
p=dir('*.txt');
nFiles=numel(p);
A_cat=[]; % A_cat=zeros(500000,30);
for k=1:nFiles
disp(size(A_cat)); %% you can check the no. of rows is increasing
%A_cat=[A_cat;A]; %% every cycle, matrix changes its size!!!
A_cat=vertcat(A_cat,A);
end
toc

KSSV on 23 Feb 2021
Edited: KSSV on 23 Feb 2021
close all; clc;
tic
p=dir('*.txt');
nFiles=numel(p);
A_cat=cell(nFiles,1); % A_cat=zeros(500000,30);
for k=1:nFiles
disp(size(A_cat)); %% you can check the no. of rows is increasing
%A_cat=[A_cat;A]; %% every cycle, matrix changes its size!!!
A_cat{k} = A;
end
A = vertcat(A_cat{:}) ;
toc
SA on 23 Feb 2021
do you think the other possibility to run the code faster?
tic;
P_avg=cell(1,30);
for j =1:30
P_dat = buffer(A(:,j),500); %% cut the 500 elements*1000 of a single sensor
P_m=mean(P_dat,2);
P_avg{j}=P_m;
end
mn_dat = horzcat(P_avg{:}) ;
toc;