How can I create a for loop to remove certain columns from different numerical arrays?

I have a series of plain text files that I need to import into matlab. Matlab imports these files as numerical arrays, and I only want the 3rd and 5th columns of each file. I have a for loop that imports each file into matlab and makes it a numerical array, but I want to take that further and remove the columns I don't want, and then save the new files back to the directory. Here's the code I have so far:

>> files = dir('*.pck'); %this creates a string of all the files of a specific extension
%  in a directory. This part works fine.
>> for i=1:21 %just the number of files I have in this specific case. This also works fine.
eval(['load ' files(i).name]); %I was only able to do this after 3 hours of googling.
%  It loads the files, makes each one a variable with the file's name as the variable name,
%  it works perfectly.

If I end the loop there then all the files I need are loaded and I can filter each one and save each one by hand, but it feels like I should be able to do this with a loop, I just don't know how to do it. The only thing I can think to try is:

files(i).name = files(i).name(:,[3,5]); 

in the same loop hoping it would do make new variables with only the 3rd and 5th columns, but that doesn't work.

Any help at all would be greatly appreciated.

Answer 1

[Walter Roberson]

projectdir = '.';    %or directory where the files are
dinfo = dir('*.pck');
filenames = fullfile(projectdir, {dinfo.name});
nfiles = length(filenames);
for K = 1 : nfiles
    thisfile = filenames{K};
    thisdata = load(thisfile, '-ascii');
    thisdata = thisdata(:,[3 5]);
    [~, basename, ~] = fileparts(thisfile);
    newname = fullfile(projectdir, [basename '.txt']);
    save(newname, 'thisdata', '-ascii');
end

No dynamic variable names used.

[Alexander Simpson]

Thank you so much! The only issue I have now is that the outputted files only have random symbols in them instead of the numbers they should have, but I'm sure I couldplay around with it to figure out why that is.

Do you have any tips on how a complete beginner could learn how to do stuff like this in MATLAB, because all the resources I found were really confusing?

Thank you so much though.

[Walter Roberson]

I fixed the code.

FAQ can help.

Also http://www.mathworks.com/matlabcentral/answers/8026-best-way-s-to-master-matlab

[Alexander Simpson]

Thank you so much!