Thread Subject:

Is there a way to tell when a warning happens?

Instead of explicitly checking for singular matrices, and other things that cause warning messages, it would be convenient to write the code so that it just runs, but IF a warning occurs, I can test it and take corrective actions.

Questions:
Is there a way to tell if any warning has occurred?
The same could be asked about errors, but they just stop the program.

Does the answer to the question have to do with the lastwarn() command?

Does anyone have an example that might help me write this loop:

     for counter=1: lots of thing
              do some processing
              if a warning occurred
                      disp('set a break here and see what to do, or test for singularity...');
              end
    end


Thanks for your expertise.


[no, this is not for homework... ;-) ]

% Okay, so this works, but seems clumsy:
lastwarn('none');
% Processing here...
checkForWarning = lastwarn();
if ( strcmp(checkForWarning,'none') ~= 1 )
    % Test for poorly conditioned matrices:
   validity = 0;
end

Better insights appreciated.

In article <kqkgcn$lbd$1@newscl01ah.mathworks.com>,
 "Pat Finder" <pfinder@netacc.net> wrote:

> % Okay, so this works, but seems clumsy:
> lastwarn('none');
> % Processing here...
> checkForWarning = lastwarn();
> if ( strcmp(checkForWarning,'none') ~= 1 )
> % Test for poorly conditioned matrices:
> validity = 0;
> end
>
> Better insights appreciated.

Hi "Pat",

Something very much like that (essentially identical) is what I did in
my intersections.m. It was the best I could come up with.

Doug

--
Doug Schwarz
dmschwarz&ieee,org
Make obvious changes to get real email address.

"Pat Finder" <pfinder@netacc.net> wrote in message
news:kqkdl2$e3j$1@newscl01ah.mathworks.com...
> Instead of explicitly checking for singular matrices, and other things
> that cause warning messages, it would be convenient to write the code so
> that it just runs, but IF a warning occurs, I can test it and take
> corrective actions.
>
> Questions:
> Is there a way to tell if any warning has occurred?

Yes, LASTWARN.

> The same could be asked about errors, but they just stop the program.
>
> Does the answer to the question have to do with the lastwarn() command?

Yes.

lastwarn(''); % Reset the last warning state
codeThatMayIssueWarning;
[warnmsg, warnid] = lastwarn;
if ~isempty(warnmsg)
    % handle issued warning
end

Alternately, if you know what condition(s) will cause the warning to be
issued, you could check those conditions ahead of time.

if isreal(x) && isreal(y)
   plot(x, y);
else
    plot(real(x), real(y));
end

> Does anyone have an example that might help me write this loop:
>
> for counter=1: lots of thing
> do some processing
> if a warning occurred
> disp('set a break here and see what to do, or test
> for singularity...');
> end
> end
>
>
> Thanks for your expertise.
>
>
> [no, this is not for homework... ;-) ]

--
Steve Lord
slord@mathworks.com
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