MATLAB Answers


Unable to do work through a loop of subdirectories

Asked by Clifford Shelton on 29 Dec 2012

I'm having mucho problems trying to get this to work: I'm trying to do some work while looping through a group of sub-directories.

I am not getting any error messages, but I am not able to complete the plotting that I am trying to do for a group of excel files that are located in various folders that are all sub-folders of the C:\data folder.

Any help is MOST appreciated. I have been stumped on this for a good part of the week! Here is the code that I have so far:

echo on;
folder = 'c:\data';
wantedfiles = {'Angels' 'Diamondbacks' 'Orioles' 'Royals' 'Yankees' 'Mets' 'Giants'};
subdirs = dir(folder);
subdirs(~[subdirs.isdir]) = [] ; 
numberOfFolders = length(subdirs);
if numberOfFolders <= 0
    uiwait(warndlg('Number of folders = 0!'))
for K = 1 : numberOfFolders
  thissubdir = subdirs(K).name;
  if strcmp(thissubdir, '.') || strcmp(thissubdir, '..')
  subdirpath = [folder '\' thissubdir];
    for L = 1 : length(wantedfiles)
      fileToRead1 = fullfile(subdirpath, [wantedfiles{L} '.xls'] );
    if exist(fileToRead1, 'file')== 0
      [numbers, strings, raw] = xlsread(fileToRead1, sheetName);
  if ~isempty(numbers) =  numbers;
if ~isempty(strings) && ~isempty(numbers)
    [strRows, strCols] = size(strings);
    [numRows, numCols] = size(numbers);
    likelyRow = size(raw,1) - numRows;
    % Break the data up into a new structure with one field per column.
    if strCols == numCols && likelyRow > 0 && strRows >= likelyRow
        newData1.colheaders = strings(likelyRow, :);
% Create new variables in the base workspace from those fields.
for i = 1:size(newData1.colheaders, 2)
    assignin('base', genvarname(newData1.colheaders{i}),,i))
subplot (2,1,1), plot(Score,Allow)
title('Testing to see if it works');
subplot (2,1,2), plot(Allow,Score)
title('Well, did it?');


assignin() and genvarname() ? Uggh! Why not just toss everything into a structure, or a cell array perhaps?

What happens when you use the debugger to step through the program? What part seems to be going wrong ?


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3 Answers

Answer by Matt J
on 29 Dec 2012
Edited by Matt J
on 29 Dec 2012

Since all the wantedfiles seem to have distinct names, why not just put the entire directory tree under c:\data on the MATLAB path


and remove it later if desired.

If everything under c:\data is on the path, you can just read each file by specifying its raw name alone, without prepending the file's full directory path address.


Answer by Image Analyst
on 29 Dec 2012
Edited by Image Analyst
on 29 Dec 2012

Your code won't find .xls files that are more than one subfolder deep. Is that the problem? If so, Matt's suggestion of addpath(genpath) will fix that. Though, I'd not use addpath, just use genpath, and construct the full path as I go down the list of folders - it's just a difference in style/preference. If you use addpath() and want to remove it afterwards like he said, you can use


Otherwise, if that's not the problem, say exactly what the problem is. Does it hang/never finish/infinite loop? What exactly does "not able to complete the plotting" mean?

Oh yeah! One other quirk that you wouldn't be aware of at first, until it bites you. The upper left cell of the three cell arrays you get from xlsread() DO NOT ALL START AT THE SAME EXCEL CELL. This is unexpected, at least by me. So you can't just put Excel in R1C1 mode and read off the row and column number and expect to find your data in that row and column number of your cell array. I can hear you saying "What!?!?" - well it's true. Each starts at the upper left cell of where it's data type starts in the worksheet. So if you have a blank row 1, and a blank column1, and column headers in going from B2 to H2, and strings going down column B and the numbers in C3 to H50, then cell (1,1) of the string and raw cell arrays corresponds to cell B2 of your workbook and cell (1,1) of your numbers cell array corresponds to cell C3 - a completely different cell in Excel. So don't think that you can just say strings(4,5) and numbers(4,5) and think they both refer to the same cell E4 in Excel, because they don't - neither one does (in my example). Take time to understand this!

I also second Walter's guidance not to use assignin. There's no reason why you can't reuse the same variable. If you need to save them for use outside the loop for some reason, put them into different cells of a cell array.

  1 Comment

Ok thanks for the help everyone. Sorry if I'm not clear as to what "won't work".

When I am debugging the program it seems to just ignore completely my commands to plot a graph of the two variables 'Score' and 'Allow'.

I am not sure as to why the program I wrote just seems to ignore the plot commands.

After trying to debug the code I listed above..I'm still in the dark. If the files I'm trying to import are being located, then why won't the plot be created?

And if the files are not being located, then why won't I get an error when I call the command to plot the data??

Very confused!

Answer by Matt J
on 29 Dec 2012
Edited by Matt J
on 29 Dec 2012

It's not clear from the code you've shown what the connection is supposed to be between the variables Score/Allow and the data in your files. You don't assign the data from the files to these variables anywhere that we can see.

In any case, it seems likely that Score and Allow are []. That would cause PLOT to ignore them. Did you examine the contents of Score and Allow before plotting them, (e.g., using OPENVAR or displaying them directly at the command line or at the K>> line) ?


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