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I want to do loop operation of these files but fail to get the desired result. Can anyone help me to figure out the problem?

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SA
SA on 14 Apr 2021
Edited: SA on 16 Apr 2021
After the operation, I wish to get the values as in the table:
The script that I work on, can't store/save the data as in the table format.
p = dir('f*.txt');
nFiles = numel(p);
counter=0;
for kk = 1:nFiles
counter= kk+1;
fileID1 = fopen(p(kk).name,'rt');
C_data = textscan(fileID1,'%f');
f1 = cell2mat(C_data); % A = dlmread(p(k).name);
%A_cat{kk} = A; disp(size(A_cat));
fclose(fileID1);
val = cell(1, nFiles-1); % Memory Pre-allocation
for i = counter: nFiles
fileID2 = fopen(p(i).name,'rt');
C_data = textscan(fileID2,'%f');
f2 = cell2mat(C_data); % A = dlmread(p(k).name);
fclose(fileID2);
[Pyy,freq]=cpsd(f2,f2,hanning(512),[],512,500);
[Pxy,freq]=cpsd(f1,f2,hanning(512),[],512,500);
[Pxx,freq]=cpsd(f1,f1,hanning(512),[],512,500);
coh= (Pxy)./sqrt(Pxx.*Pyy);
val=real(coh(42))
%val=horzcat(val)
end
val(kk)=horzcat(val)
end
Can anyone help to fix the issues? Thank you in advance.

Accepted Answer

Mathieu NOE
Mathieu NOE on 14 Apr 2021
hello
I tweaked a bit your code , if fact it was simpler in my opinion to do the full 4 x 4 loops instead of doing the specific counter condition
now there is one point that surprises me, its the diagonal of your matrice . the autocorrelation of each element with itself should be 1 and not zero (and it's what I get) - so I wonder about this point. of course we can change the code to force the diagonal to be zero but that sounds strange to me
p = dir('f*.txt');
nFiles = numel(p);
counter=0;
for kk = 1:nFiles
%counter= kk+1
fileID1 = fopen(p(kk).name,'rt');
C_data = textscan(fileID1,'%f');
f1 = cell2mat(C_data); % A = dlmread(p(k).name);
%A_cat{kk} = A; disp(size(A_cat));
fclose(fileID1);
%val = cell(1, nFiles-1); % Memory Pre-allocation
for i = 1: nFiles
fileID2 = fopen(p(i).name,'rt');
C_data = textscan(fileID2,'%f');
f2 = cell2mat(C_data); % A = dlmread(p(k).name);
fclose(fileID2);
[Pyy,freq]=cpsd(f2,f2,hanning(512),[],512,500);
[Pxy,freq]=cpsd(f1,f2,hanning(512),[],512,500);
[Pxx,freq]=cpsd(f1,f1,hanning(512),[],512,500);
coh= (Pxy)./sqrt(Pxx.*Pyy);
val(kk,i)=real(coh(42)) ;
end
end
% gives :
val =
1.0000 0.6725 -0.2602 0.3779
0.6725 1.0000 0.1127 0.2854
-0.2602 0.1127 1.0000 0.0763
0.3779 0.2854 0.0763 1.0000
  5 Comments
SA
SA on 15 Apr 2021
Thanks for your question. File size is big as I consider longer time (10,000+ seconds). I want to check the Real Coherence value at a specific frequency(say @40Hz =(coh(42))). Here, the sampling frequency is chosen fs=500 and 'noverlap' left blank which matlab set 50% (default).
so, I tried the following scripts.
clc; close all;
p = dir('f*.txt');
nFiles = numel(p);
counter=0;
val = zeros(nFiles); % Memory Pre-allocation
for kk = 1:nFiles
%counter= kk+1
fileID1 = fopen(p(kk).name,'rt');
C_data = textscan(fileID1,'%f');
f1 = cell2mat(C_data); % A = dlmread(p(k).name);
fclose(fileID1);
for i = (kk+1): nFiles
fileID2 = fopen(p(i).name,'rt');
C_data = textscan(fileID2,'%f');
f2 = cell2mat(C_data); % A = dlmread(p(k).name);
fclose(fileID2);
[Pyy,~]=cpsd(f2,f2,hanning(512),[],512,500);
[Pxy,~]=cpsd(f1,f2,hanning(512),[],512,500);
[Pxx,~]=cpsd(f1,f1,hanning(512),[],512,500);
coh= (Pxy)./sqrt(Pxx.*Pyy);
realCoh=real(coh(42));
val(kk,i)=val(i,kk)+realCoh;
end
end
final_val=val+val'+eye(nFiles);
If I calculate the half of the symmetric matrix and adding transpose of it, it saves 60% of time. Thanks for your time.

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