Coding a program to write an M file - possible?

Hi all,

I am writing a GUI for an existing program. This program runs an M file (currently users specify which to run manually editing the code) which contains data and some calculations - there are hundreds of these M files for different users, that contain data about them. All are different (but the same, bar the numbers...) and have been created manually over a period of time.

I am writing a GUI which will provide an interface for loading these files, but also allow a user to make a new M-file based on their product.

Is there a way, once the user has entered the data about their product in the GUI, that I can get the program to write an M-file script, for their product?

e.g User enters mass = 610, length = 1200 and program makes script and writes m = 610; l=1200; (continues for more parameters) then saves the .m file where the others are stored.

I have easily got the GUI to load an existing m-file and populate the GUI for the user to edit it but I have no idea how I can program the GUI/program to write a script based on new data.

Thanks,

Matt.

[Henry Giddens]

Hi Matt,

Isn't a '.m' file essentially just a text file? If so why not just write your program to write the code to a a text file, then change the extension to '.m'?

[Matt]

This is what I have been considering... but, how?

If the user enters mass as 610 (stored a 'mass') my text file needs to say 'm = 610'

Forgive my ignorance but how would I do this? I can't write 'm = mass' or 'm = num2str(mass)' of course...!

[Matt]

I suppose I could use something like

fprintf(['m = ' num2str(mass)]..........etc.)

[Matt]

This concept works (to edit product, could easily write new file for new product) but as said below perhaps I need to reconsider the approach...

      % Specify a Variable
      mass = 610

      % Open Text File (could be .m - rename to .txt first)
      fileID = fopen('client1produt1.txt','w');

      % Edit Text File
      fprintf(fileID,['m = ' num2str(mass)]);

      % Close Text File
      fclose(fileID);

      % Rename File to Create M File
      movefile('client1produt1.txt','client1produt1.m', 'f')

      % Run Created File to Check Working
      client1produt1

Answer 1

[Image Analyst]

I'd do like Guillaume suggests. Have a "main" m-file, with a constant name that reads in the mat file, which has a name where the parameters are coded into it and into the filename. So you'd do something like

% Create mat file
baseFileName = sprintf('m%d, l%d.mat', m, l);
fullMatFileName = fullfile(folder, baseFileName);
save(fullMatFileName, 'm', 'l');

Now, in main.m:

% Get the mat file they've been given
filePattern = fullfile(folder, 'm*.mat');
files = dir(filePattern);  % Hopefully returns only 1, but could return more if there are more.
thisMatFileName = fullfile(files(1).folder, files(1).name); % Get first name
% Open it
storedStructure = load(thisMatFileName);
% Extract m and l
m = storedStructure.m;
l = storedStructure.l;

Of course if they have been given more than one .mat file, you should ask them which one they want to use. I'd call uigetfile() for that, or you could put the filenames into a cell array and use menu().

[Matt]

This is by far the best solution, as Guillaume suggested.

Thanks very much for your example - I'll have a play to familiarise myself with the approach, then try to implement it.

Deep down I knew it was the best solution, but thought it was trickier to implement than it seems.

All is not lost, i've just taught myself how to write a text file, very handy, and can now make a new script using GUI data - may be useful one day.

[Matt]

Thanks - based on this and some other recent questions I have revamped my program to save and load data from .mat files instead of .m files.

Now I no longer need to use the run command to run .m files in other folders, nor write an .m file when a user adds details for a new product, and my data handling is much better.

It's not quite done, but I think i'm almost there!

Thanks very much!

Answer 2

[Guillaume]

You can of course write any type of file you want with matlab low level IO functions. However, if I were you I would change my approach.

If the only thing that changes between m files is some parameters (i.e. the actual processing code is the same), I would rewrite it so that it actually loads those parameters (from a mat file, text file, database, whatever is more practical) at start and uses these. That way the m file never changes and you distribute the configuration file to the user.

[Matt]

Thanks - this is what I feared I may have to do, but was trying to take a shortcut as performance is beyond good enough already and is not a concern. Just getting the GUI version of the program working and keeping the basis of its operation identical is a priority.

I'll have a think about my approach and add another comment in a while.

[Guillaume]

As an addendum and an answer to your comment to the question, the simplest way to write your 'm = somevalue' into a file (you can just write it straight with .m extension, no need to rename):

mass = 620; comes from your GUI
fid = fopen('C:\somewhere\filetowrite.m', 'wt');  %open file for writing (as text so line endings are correct for your platform)
fprintf(fileid, 'm = %f\n', mass);  %if mass is always integer replace %f by %d

However, it would be much simpler in the long term to have the two separate files as I've suggested. It also should not affect performance at all. It's also a lot more flexible, you can actually update the processing code (e.g. fix bugs) without having to recreate all the individual user files.

[Matt]

Thanks very much - deep down I knew it was the best solution, but thought it was trickier to implement than it seems.

RE writing a script - I managed to do something similar, as seen in my comment on my original post. Handy to know that you can write .m directly, thanks.