Can I suppress command window output of a function in Matlab?-CodePudding

In Matlab I often use functions in my script that output something to the command window in one or several ways, for instance like this:

function output = mySubFunction(input)
    disp(['the input is: ', num2str(input)])
    output = input * 2;
    disp(['the output is: ', num2str(output)])
end

If I now use this function in my script it would look something like this:

data = 5;
disp('applying transformation...')
transformation = mySubFunction(data);
disp(['the result of the transformation is: ', num2str(transformation)])

This is of course a very simple example, in fact the functions are often quite complicated and give a lot of output. In this case, to keep a better overview of what is going on in my main script using my command window, I would like to suppress the disp() functions in my mySubFunction. Is there any way that I can do this simply from my main script (that is, without diving into possibly very complicated functions and subfunctions to comment out all disp() functions or insert semicolons)?

CodePudding user response：

The typical way to do this in any language as far as I'm concerned, not just matlab / octave, is to have a 'debug' or 'verbose' variable present, which is checked against an if statement and decides whether to print those logs. The if statement could be used in the relevant code directly, or wrapped inside a 'prettier' function responsible for doing the logging.

This variable may be passed explicitly to the function, or it could be a global variable. If you plan to run your script directly from the shell rather than directly from a matlab/octave environment, it could even be detected from from a shell-defined environmental variable. Alternatively, it could be read from a config file. It all depends on your use case.

For the sake of an example, here is your session, transformed as above, using the global variable approach.

%% in file mainScript.m 
global VERBOSE
VERBOSE = true;
data = 5;
if VERBOSE, disp('applying transformation...'); end
transformation = mySubFunction(data);
if VERBOSE, disp(['the result of the transformation is: ', num2str(transformation)]); end

%% in file mySubFunction.m 
function output = mySubFunction(input)
    global VERBOSE
    if VERBOSE, disp(['the input is: ', num2str(input)]); end
    output = input * 2;
    if VERBOSE, disp(['the output is: ', num2str(output)]); end
end

CodePudding user response：

I believe you want evalc.

From the MATLAB-documentation (the function is similar in Octave):

Use the "evalc" function to redirect all the output displayed on the command window to a variable. This will not suppress figures, but it does allow you to prevent print statements from being displayed in the command window.

As an example:

[results, output] = evalc('mySubFunction(3)');

This displays nothing but stores the following variables in the workspace:

>> [results, output] = evalc('mySubFunction(3)');
>> ans
ans = 6
>> output
output = 6
>> results
results = the input is: 3
the output is: 6