"vertcat" error with array of strings

I have an array of strings, which is used to store a collection of filenames to retrieve data. Depending on the task at hand, sometimes I need to access the data from only certain files, in which case I would like to comment out some filenames from the array.

When I do that, I get an error saying:

 Error using ==> vertcat
 CAT arguments dimensions are not consistent.

Here's a test program that illustrates the problem:

fprintf('\n\n BEGIN \n\n');

input_file_array = {...  
                    'test1.txt',...
                    'test2.txt', ...
                    %'test3.txt', ...
                    'test4.txt', ...
                    };               

fprintf('\n\n DONE \n\n');

Note that I get the error only when there is a continuation of the array elements after the commented line (but if I were to comment out both test3 and test4, I get no error).

I'm using Matlab R2007a.

Answer 1

[Walter Roberson]

You can't do that. The commented out line is treated as a blank line, which switches over the parsing to vertical concatenation, the same as if you were using { 'test1.txt', ... 'test2.txt' 'test4.txt' }

which would be equivalent to trying to do

{ 'test1.txt', 'test2.txt'; 'test4.txt'}

What I suggest is that you switch over to vertical concatenation anyhow. Transpose the resulting cell array if you need to:

input_file_array = {...  
                  'test1.txt';...
                  'test2.txt'; ...
                  %'test3.txt'; ...
                  'test4.txt'; ...
                  };

The % will be treated as a blank line with the implied vertical concatenation, but since you are using vertical concatenation anyhow you don't run in to a conflict.

You can simplify this code as:

input_file_array = { 
                  'test1.txt'
                  'test2.txt'
                  %'test3.txt'
                  'test4.txt'
                  };

taking advantage of the implicit vertical concatenation.

[Andrew Newell]

I like this better than my solution.

Answer 2

[Andrew Newell]

That commented line is just like having an empty line in the middle of your command (try it!). You could do this:

input_file_array = {...  
                  'test1.txt',...
                  'test2.txt', ... %'test3.txt', ...
                  'test4.txt', ...
                  };

Answer 3

[Ksenia]

Thank you all very much for your quick and insightful replies! Such an easy explanation (and solution) for something that has been bugging me for a long time.

Appreciate you help!