Services & Resources / Wolfram Forums
-----
 /
MathGroup Archive
2007
*January
*February
*March
*April
*May
*June
*July
*August
*September
*October
*Archive Index
*Ask about this page
*Print this page
*Give us feedback
*Sign up for the Wolfram Insider

MathGroup Archive 2007

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: plot error messages are completelly missing

  • To: mathgroup at smc.vnet.net
  • Subject: [mg81038] Re: plot error messages are completelly missing
  • From: Helen Read <read at math.uvm.edu>
  • Date: Sat, 8 Sep 2007 03:59:19 -0400 (EDT)
  • References: <fbojp5$jbs$1@smc.vnet.net> <fbqqoe$7c5$1@smc.vnet.net>

Szabolcs wrote:
> 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).

I for one am glad that I no longer see those annoying "not a machine 
size real number" messages. It's no longer a problem to plot a function 
across an interval where it is not real. For example, I can now plot 
ArcSec[x] for {x,-5,5} and get a nice looking plot, or plot Sqrt[x] 
together with Sqrt[x+5] on {x,-5,5} without having to plot them 
separately and Show. To me this is an improvement.

On a somewhat related topic, I really like the new Exclusions option.

--
Helen Read
University of Vermont


  • Prev by Date: Re: [Mathematica 6.0.1] Confusing documentation on ColorData, where to get list of ColorFunctions ?
  • Next by Date: Re: [Mathematica 6.0.1] Confusing documentation on ColorData, where
  • Previous by thread: Re: plot error messages are completelly missing
  • Next by thread: Re: plot error messages are completelly missing