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MathGroup Archive 2007

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Re: plot error messages are completelly missing

  • To: mathgroup at smc.vnet.net
  • Subject: [mg81004] Re: plot error messages are completelly missing
  • From: Szabolcs <szhorvat at gmail.com>
  • Date: Fri, 7 Sep 2007 02:12:43 -0400 (EDT)
  • Organization: University of Bergen
  • References: <fbojp5$jbs$1@smc.vnet.net>

Josef Otta wrote:
> Hi all,
> 
> I have a question to a catching error messages is the evaluation of
> graphics functions in the version 6. For example, consider a function
> plotting  with non real values:
> 
> {Plot[Sqrt[x], {x, -2, 1}],
>   $MessageList}
> 
> in version 5.2 the output is a plot with these messages
> 
> {Plot::plnr, Plot::plnr, Plot::plnr, General::stop}}
> 
> If I use the same approach in the version 6.0 i get no error messages
> and that is a big problem for me. Do you have any idea how to get
> these errors?
> I do not know how to get these messages also in the cases where
> 
> Complex,  ComplexInfinity, Indeterminate, Null, Underflow or Overflow
> 
> occur in the evaluation of almost every graphics function.

I would like to know this too.  On[General::plnr] turns on this warning 
message.  However, the message is only issued when Plot encounters a 
symbolic expression.  It does not work for complex numbers, infinity etc.

And I do not understand why this new General::plnr is turned off by 
default.  Passing a completely non-numerical argument (as opposed to a 
function that evaluates to complexes in some regions) to Plot is an 
unintentional mistake in 99% of the cases.  The only time I turned off 
Plot::plnr in 5.2 was when repeatedly plotting things like Plot[Sqrt[x], 
{x, -1, 1}], but these kinds of examples do not warn with Plot::plnr any 
more in Mathematica 6 (even though it would often be useful).

Szabolcs


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