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Re: and color via PlotStyle

  • To: mathgroup at smc.vnet.net
  • Subject: [mg118541] Re: and color via PlotStyle
  • From: DrMajorBob <btreat1 at austin.rr.com>
  • Date: Mon, 2 May 2011 06:51:51 -0400 (EDT)

> But as a novice I want to know, why does Plot see the ReplaceAll?

That's because of:

Attributes@Plot

{HoldAll, Protected}

Because of the HoldAll attribute, Plot starts work with ALL its arguments  
unevaluated.

That is useful, of course, if the plot function cannot be evaluated with  
symbolic arguments.

Bobby

On Sun, 01 May 2011 05:21:52 -0500, Alan <alan.isaac at gmail.com> wrote:

> On Friday, April 29, 2011 7:33:39 AM UTC-4, Bill Rowe wrote:
>> [version 1] works as you are expecting only because the argument to
>> Plot is an explicit list. This is the only case where Plot uses
>> multiple colors.
>
> (Warning: Mathematica novice ahead.)
>
> I do not understand this statement.  Do you mean the key is
> that Plot sees a head of List rather than of ReplaceAll?
> But as a novice I want to know, why does Plot see the ReplaceAll?
> What is the rule that determines whether or not a command will
> evaluate its argument before acting on it?
>
>> Plot always evaluates its arguments by
>> first substituting a numeric value for the independent variable
>> and only after that is the expression evaluated. The consequence
>> it for the argument above, Plot does not see a list of
>> expressions. Instead it sees a list of numeric values which is
>> treated as a single function with multiple values and
>> consequently plotted in a single color.
>
> Can you please restate that.  I'm finding it opaque.
> (Also, is there no way to assign multiple colors to
> a mutiple valued function?)
>
>
>> There is no inconsistency in the behavior of Plot. The behavior
>> I am describing is well documented even if not always well understood.
>
> Can you please point to the documentation you have in mind here.
> Thanks!
>
> Alan Isaac
>


-- 
DrMajorBob at yahoo.com


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