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MathGroup Archive 1995

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Re: PlotRange Limitation?

  • Subject: [mg899] Re: PlotRange Limitation?
  • From: rubin at msu.edu (Paul A. Rubin)
  • Date: Fri, 28 Apr 1995 00:57:01 -0400
  • Apparently-to: mathgroup-send at christensen.cybernetics.net
  • Organization: Michigan State University

In article <3ni501$afg at news0.cybernetics.net>,
   martind at carleton.edu (D<martind at carleton.edu>M) wrote:
->Ok - I've got a question:
->I'm just trying to get a decent plot out of Mathematica for a function 
that
->returns some very small values.
->However, I won't worry you all with the function as the problem occurs in 
the
->Plot:
->The command:
->Plot[x*10^-29, {x, 0, 100}, PlotRange -> {0, 10^-27}]
->Gives me a little graph of nothing - the PlotRange is apparently ignored, 
and
->is treated as if I had typed {-0.5, 0.5} for the PlotRange; (I get this
->information from FullOptions).
->Now, one solution would be to scale the function up a bit and use Ticks 
to
->simulate being way down under, but I'd rather not do that - I just want 
to Plot
->where I want to Plot.
->I tried some odd replacement rules to get a FullForm that looked like it 
had
->the proper PlotRange, but when I did a Show of that Graphics object and 
then
->another FullForm, it appeared that PlotRange had secretly returned to 
{-0.5,
->0.5}.
->Is there a hidden limit on PlotRange?  Can it be changed?
->
->martind at carleton.edu
->
I think that Plot is "hardwired" to use machine precision numbers, at least 
for the plot range.  On my PC (machine precision being about 16 digits), I 
can generate the graph with the exponents -29 (-27) changed to -16 (-14), 
but when I make them -17 (-15) the override of PlotRange occurs.  My guess 
is that Plot, after converting arguments to machine numbers, sees the {0, 
10^-27} plot range as being {0., 0.}, which forces it to revert to some 
default.

Paul

**************************************************************************
* Paul A. Rubin                                  Phone: (517) 432-3509   *
* Department of Management                       Fax:   (517) 432-1111   *
* Eli Broad Graduate School of Management        Net:   RUBIN at MSU.EDU    *
* Michigan State University                                              *
* East Lansing, MI  48824-1122  (USA)                                    *
**************************************************************************
Mathematicians are like Frenchmen:  whenever you say something to them,
they translate it into their own language, and at once it is something
entirely different.                                    J. W. v. GOETHE


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