Matlab - how to catch warning released by cp2tform function

Question

I have a set of N sets of 2D points and I want to parse these N sets in order to find the affine transformation(translation, rotation, scaling including reflexion) with another set q of 2D points.

In order to do so, I am applying the Matlab function cp2tform. However, there are certain scenarios when the function gives me a warning similar to the one illustrated bellow:

Warning: The condition number of A is 117632159740.8394. 
> In maketform>validate_matrix at 328
  In maketform>affine at 163
  In maketform at 129
  In cp2tform>findAffineTransform at 265
  In cp2tform at 168

In these cases, the transformation matrix identified with the cp2tform function does not apply to the real transformation between the 2 sets of 2D points. How can I catch these situations in order to skip them? What matlab function or code should I introduce in order to catch these situations in order to be able to skip or handle them?

Answer 1

Handle Warning:

As explained here, you could convert specific warnings to errors, and trap those inside a try/catch block.

Here is an example on how to handle a specific warning (inverting a nearly singular matrix):

% turn this specific warning into an error
s = warning('error', 'MATLAB:nearlySingularMatrix'); %#ok<CTPCT>

% invoke code trapping errors
try
    A = [1 2 3; 4 5 6; 7 8 9];
    B = inv(A);
    disp(B)
catch ME
    if strcmp(ME.identifier, 'MATLAB:nearlySingularMatrix')
        fprintf('Warning trapped: %s\n', ME.message);
    else
        rethrow(ME);
    end
end

% restore warning state
warning(s);

---

Suppress Warning:

Of course if you want to suppress a warning message, you could just query the last warning issued using:

[msgstr, msgid] = lastwarn;

(or use the syntax that @Benoit_11 showed), then turn it off until temporarily inside your function:

% turn it off
s = warning('off', msgid);

% ...

% restore state
warning(s);