divideByZero warning does not show up when dividing by zero.

2011 7 29
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I am working with MATLAB 2011a, and I do not see the MATLAB:divideByZero warning appearing when I do divide by zero, though I set the divideByZero warning on with:
warning on MATLAB:divideByZero
I tried it with MATLAB 2009, and the warning appeared in this release. Unfortunately, I need to have it working on 2011a.
How can I get this warning to appear?

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Daniel Shub
Daniel Shub 2011-7-29
Loren's blog says that in r2006b 1/0 should give a warning
http://blogs.mathworks.com/loren/2006/10/18/controlling-warning-messages-and-state/
in r2011a it does not.
the cyclist
the cyclist 2011-7-29
Sorry, accidentally deleted my own comment! Here it is again, out of order with yours!
Can you give a small example of code where you would expect this warning to show up , but it doesn't? [I know that sounds trivial, but for example 1./0 will not give such a warning; it will simply report "Inf" as an answer.]
Paulo Silva
Paulo Silva 2011-7-29
by default MATLAB doesn't give warning for divisions by zero
Adrien
Adrien 2011-7-29
Thank you all for helping me. To answer your different questions:
- I tried it on a simple line of code as "1/0" and I got the warning in 2009a (once I activated the warning with "warning on MATLAB:divideByZero
"), but not in 2011a (even with the warning activated the same way).
- maybe MATLAB doesn't give warning by default for divisions by zero, but it should if it is activated. Still it doesn't in the 2011a release.
It's still quite weird to me.

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the cyclist
the cyclist 2011-7-29

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The following is in the Release Notes for R2009b. However, explicitly turning on the warning does not enable it for me, in R2011a. I don't see the warning on the screen, or using the lastwarn() function.
http://www.mathworks.com/help/releases/R2009b/pdf_doc/matlab/rn.pdf
Divide By Zero and Log Of Zero Warnings Off By Default
MATLAB no longer displays Divide by zero and Log of zero warnings unless you explicitly enable them with the following commands:
warning on MATLAB:divideByZero
warning on MATLAB:log:LogOfZero
This only affects the display of the warning message on the screen; the warning status is still updated as usual.

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Adrien
Adrien 2011-7-29
I tried this and am still not getting the warning, neither on the control window, neither with the lastwarn function. It's surprising the behaviour of MATLAB doesn't match what they are explaining here...
Adrien
Adrien 2011-7-29
My bad, there is no contradiction : these document just explain how to do it with the 2009 release, which works. I am going to look for an equivalent document for the 2011 release.

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更多回答（2 个）

the cyclist
the cyclist 2011-7-29

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I have R2010a, R2010b, and R2011a on my machine. None of them give a warning for 1/0. If 2009 gave the warning, looks like maybe the behavior changed at 2010a? Could scan the release notes.

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Adrien
Adrien 2011-7-29
I just tried it again, and there is a warning for a simple code as 1/0 with Matlab 2009a... but not with 2011a.

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Walter Roberson
Walter Roberson 2011-7-29

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Enter the command
warning
It will show you the warnings that exist but which are not set to 'on'.

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