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Read in files with loop

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I have the code below which reads in the data to log200. The thing is, I also need to read in other data too.
I need log200, log225, log250, in increments of 25 up to log900
How can I take my current working script which reads in log200, and replace it with a loop so that I do not have to copy and paste dozens of times?
clear
clc
lastn=1;
log200=importdata('C:/Users/Ben/Desktop/log.200_equil', ' ', 20, 0);
log200_cell = log200.data(:,6);
log200_cell = log200_cell(1:end-lastn,:);
log200_density_average=mean(log200_cell)

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Benjamin Cowen
Benjamin Cowen on 10 Aug 2018
All I care about is the 6th column from each log file. I skip the first 20 lines of the file, and just want the average value of the 6th column from each log file. That way, I can just plot the average values at each corresponding X.
Stephen Cobeldick
Stephen Cobeldick on 10 Aug 2018
@Benjamin Cowen: sure. It would help a lot if you uploaded a sample file or two, by clicking the paperclip button.
Benjamin Cowen
Benjamin Cowen on 10 Aug 2018
There is a sample file in my original question. By the way, I tried your solution below, and it seems like you know what you are talking about. I appreciate the help. I have a data structure (I guess), labeled C. This is {1,29}. Each one of these has a matrix in it called data. First I want to delete the last line from each matrix, which my original code did, and then take the average of the last 100 points in the 6th column. I tried doing some of this with my original solution. How do I apply it here?

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Accepted Answer

Stephen Cobeldick
Stephen Cobeldick on 10 Aug 2018
Edited: Stephen Cobeldick on 10 Aug 2018
Simpler to use indexing and fullfile:
D = 'C:/Users/Ben/Desktop/';
S = dir(fullfile(D,'*_equil')); % where is the file extension?
N = numel(S);
C = cell(1,N);
M = nan(1,N);
for k = 1:N
F = fullfile(D,S(k).name);
fprintf('Now reading %s\n',F);
T = importdata(F,' ',20);
C{k} = T.data;
M(k) = mean(T.data(1:end-1,6));
end
All data will be in cell array C, and M should be all of the mean data joined together into one numeric vector. You will need to check the options for importdata: I don't have this so I can't run this code!
"... then take the average of the last 100 points in the 6th column"
If you really want the last 100 points, then perhaps you will need this:
D{k} = mean(T.data(end-100:end-1,6));

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Stephen Cobeldick
Stephen Cobeldick on 10 Aug 2018
@Benjamin Cowen: you are right, I re-used the variable name D for one of the cell arrays. I changed it in my answer, please check it again. You will need to define the path D again (i.e. run the code from the start!).
Benjamin Cowen
Benjamin Cowen on 10 Aug 2018
I think you have helped enough. I got a good enough start on this problem. thanks for all the help!
Stephen Cobeldick
Stephen Cobeldick on 10 Aug 2018
@Benjamin Cowen: any time, it was a pleasure! It is nice working with people who show an interest, and who actually respond to our replies :)
Good luck with the code and come and ask us anything!

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More Answers (2)

Paul Shoemaker
Paul Shoemaker on 10 Aug 2018
Edited: Paul Shoemaker on 10 Aug 2018
You could wrap it in a FOR loop and employ the "eval" function.
lastn=1;
clear
clc
for idx = 200:25:900
temp = importdata(['C:/Users/Ben/Desktop/log.' num2str(idx) '_equil'], ' ', 20, 0); % Use num2str to replace "200" with the idx value
temp = temp.data(:,6);
temp = temp(1:end-lastn,:);
eval(['log' num2str(idx) '_density_average=mean(temp);']); % Now evaluate to create desired output
end
In the above, I'm assuming that only the "mean" calculation is desired and everything prior to that is just processing that you can throw away. If not, you can use "eval" on those as well.

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Image Analyst
Image Analyst on 10 Aug 2018
Do not use eval(). To read in a bunch of files called "log.***" use one of the two code samples in the FAQ: https://matlab.wikia.com/wiki/FAQ#How_can_I_process_a_sequence_of_files.3F

  2 Comments

Benjamin Cowen
Benjamin Cowen on 10 Aug 2018
How do I use this code, below, which reads in each file, and perform the above operations still?
lastn=1;
clear
clc
% Specify the folder where the files live.
myFolder = 'C:/Users/Ben/Desktop/';
% Check to make sure that folder actually exists. Warn user if it doesn't.
if ~isdir(myFolder)
errorMessage = sprintf('Error: The following folder does not exist:\n%s', myFolder);
uiwait(warndlg(errorMessage));
return;
end
% Get a list of all files in the folder with the desired file name pattern.
filePattern = fullfile(myFolder, '*_equil'); % Change to whatever pattern you need.
theFiles = dir(filePattern);
for k = 1 : length(theFiles)
baseFileName = theFiles(k).name;
fullFileName = fullfile(myFolder, baseFileName);
fprintf(1, 'Now reading %s\n', fullFileName);
end
Image Analyst
Image Analyst on 10 Aug 2018
It doesn't look like your file pattern is correct, but it looks like you have a working answer from Stephen. However, if you're still interested in using the FAQ code...
I think the file pattern should have been 'log.*' will work for "log.300_equil" if the extension if of the form "nnn_equil".
And 'log*.txt' will work for "log.300_equil.txt" if your files have '.txt' extensions like the one you attached.

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