How to save to a specific filename in a for loop

So I have been having this issue for a while and I really would like to figure it out. I have a lot of data at 15 minute intervals and I want it over and hour. I have no issue doing this. The function that I call creates the correct OUTPUT. My issue is that I am not able to save the OUTPUT to a filename that takes the form ['data_1hr_2013',num2str(k)]. I need to figure out a way to save OUTPUT with the filename I create. Any help would be grealy appreciated. I could have sworn I used to do this all the time in previous versions of MATLAB. I am using 2014a now.

for k = 7:12

    matFileName = sprintf('data_15min_2013%d.mat', k);

      if exist(matFileName, 'file')
        matData = load(matFileName);
      else
        fprintf('File %s does not exist.\n', matFileName);
       end
      
   OUTPUT = Conv15min2hr(eval(['matData.data_15min_2013',num2str(k)]));

    save(['data_1hr_2013',num2str(k)],OUTPUT);

end

[Star Strider]

Do you get an error, or is the problem that when you look in the appropriate directory (or search) you can’t find the file?

[Jason]

I did get an error and I have now fixed this issue. So one more question. When I load data_1hr_2013.mat into the workspace it is labeled OUTPUT. Is there way to just call it data_1hr_20137 instead of OUTPUT?

Answer 1

[Image Analyst]

What on earth is that eval statement supposed to do???

Plus, OUTPUT should be in single quotes when you send it into the save function.

baseMatFileName= sprintf('data_1hr_2013%d.mat', k);
fullMatFileName  = fullfile(folder, baseMatFileName); % folder = pwd or wherever...
save(fullMatFileName, 'OUTPUT');

[Jason]

I had to use the eval to pull the correct file into the function. Is there a better way for me to do this?

[Image Analyst]

I'm sure there is, but I don't know what you want to do. The eval() is doing essentially like what would happen if you typed the name of that file onto the command line. What does that do? Does it return the structure that is stored in your .mat file? What kind of input is the function Conv15min2hr() expecting?

Answer 2

[Robert Cumming]

BTW: eval is rarely the best choice...

I think you want:

% create your fieldname (sprintf is faster than str2num and joining using []
varName = sprintf ( 'matData.data_15min_2013%i', k );
% store your data in a struct using the above name:
matData.(varName) = OUTPUT;
% save the to file
save ( fullMatFileName, 'matData' );
% remove the field to avoid it being added to in the next loop.
matData = rmfield ( matData, varName );