No pre-defined input in a function

Good evening,

I'm about to do some experiments and afterwards I would like to do exactly the same data processing (graphs and such), so I figured a function would be in order. However, for convenience I would like the input of the function to be dynamic, if that is possible.

So if I input name of subject A, the function loads A's data and does calculations.

My current code is:

function experiment(subjectname)
subject.data = load(subjectname);

end

And I have a script, which does nothing at the moment but try to use the function:

experiment(subjectA)

When running the script, I get the following error: "Undefined variable "subjectA" or function "experiment""

Both the experiment.m and subjectA.mat are in my MATLAB directory.

Answer 1

[Image Analyst]

You need to pass in the filename as a string.

baseFileName = 'subjectA.mat';
% folder might be pwd or whatever....
fullFileName = fullfile(folder, baseFileName);  
if exist(fullFileName, 'file')
  % File exists, use it
  experiment(fullFileName);
else
  % File doesn't exist - alert user.
  errorMessage = sprintf('Warning: file not found:\n%s', fullFileName);
  uiwait(warndlg(errorMessage));
end

[Tobias]

So instead of changing my input for the function, I change:

baseFileName = 'subjectA.mat';

to

baseFileName = 'subjectB.mat';

And this change would affect fullFileName and thereby the experiment function and the data processing which are being done?

[Image Analyst]

Yes. You can make it whatever you want. You can use uigetfile() if you want, or even use sprintf:

for k = 'A' : 'Z'
  baseFileName = sprintf('subject%c.mat', k)
end

[Tobias]

Alright, I will try to implement that next time I have time to sit down with Matlab. I appreciate your feedback!

[Tobias]

There must have been a misunderstanding somewhere in our communication. The code works nearly perfect, but rather than using the workspace values I have saved in subjectA.mat, it simply creates a variable baseFileName which equals the raw text "subjectA.mat" ..

Say subjectA.mat contains a 3 x 2 matrix - is there anyway I can make baseFileName load that data and not just the filename itself?

[Image Analyst]

Your function opens the mat file and reads the contents. What you're missing is to pass it back

function subject = experiment(subjectname)

or to load it into a global variable with setappdata() or the global keyword.