indexing a loop to run through multiple files

I have experimental data in multiple csv files.

Ive written the code I want and checked this works by only inputting 1 specific file, but now I am trying to write in a loop to do the same for all the files. I am struggling with the indexing to get this to work, could anybody help?

%% input csv files
file = dir('*.csv'); %read the files into matlab
num_files = length(file); %record how many files have been found
[~, index] = natsort({file.name}); %sort the files into order
filelist = file(index);

%% Calculate granular temperature 
for a = 1:length(num_files)
%read the table into matlab
table = table2array(readtable(filelist(a).name));
%save the particle ID's and velocity components
T = table(:, [1:4]);
%calculate resultant velocity for each particle (sqrt of the velcoities squared)
ResV = sqrt((T(:,2).^2) + (T(:,3).^2) + (T(:,4).^2));
%calculate mean resultant velocity of all the particles
ResVav = mean(ResV)
%calculate the average granular temperature 
GTav = mean(ResV-ResVav)
end 

Answer 1

[Yongjian Feng]

Try this:

%% input csv files
file = dir('*.csv'); %read the files into matlab
num_files = length(file); %record how many files have been found
sorted = sort({file.name});

for a = 1:length(num_files)
%read the table into matlab
table = table2array(readtable(sorted{a}));
%save the particle ID's and velocity components
T = table(:, [1:4]);
%calculate resultant velocity for each particle (sqrt of the velcoities squared)
ResV = sqrt((T(:,2).^2) + (T(:,3).^2) + (T(:,4).^2));
%calculate mean resultant velocity of all the particles
ResVav = mean(ResV)
%calculate the average granular temperature 
GTav = mean(ResV-ResVav)
end 

[C.G.]

Thankyou for your response.

I have tried the sort function you use but it doesnt sort my files into the correct order, it has done 1,10,11... etc.

Also I ran your code and it is still telling me that a is 1, when num_files is 40. This is what it was doing when I tried myself

[Yongjian Feng]

I see. Just a small mistake there.

%% input csv files
file = dir('*.csv'); %read the files into matlab
num_files = length(file); %record how many files have been found
sorted = sort({file.name});
for a = 1:num_files
%read the table into matlab
table = table2array(readtable(sorted{a}));
%save the particle ID's and velocity components
T = table(:, [1:4]);
%calculate resultant velocity for each particle (sqrt of the velcoities squared)
ResV = sqrt((T(:,2).^2) + (T(:,3).^2) + (T(:,4).^2));
%calculate mean resultant velocity of all the particles
ResVav = mean(ResV)
%calculate the average granular temperature 
GTav = mean(ResV-ResVav)
end 

[C.G.]

Thank you that works for me now.

Just another question, but in each iteration of the loop I want the variable GTav to save so I can plot this up. Is there a way to save this value each time?

[Yongjian Feng]

Yes. Try this:

%% input csv files
file = dir('*.csv'); %read the files into matlab
num_files = length(file); %record how many files have been found
sorted = sort({file.name});
result = [];
for a = 1:num_files
%read the table into matlab
table = table2array(readtable(sorted{a}));
%save the particle ID's and velocity components
T = table(:, [1:4]);
%calculate resultant velocity for each particle (sqrt of the velcoities squared)
ResV = sqrt((T(:,2).^2) + (T(:,3).^2) + (T(:,4).^2));
%calculate mean resultant velocity of all the particles
ResVav = mean(ResV)
%calculate the average granular temperature 
GTav = mean(ResV-ResVav);
result(end+1) = GTav;
end 

result

[C.G.]

Thank you for your help!