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MathGroup Archive 2003

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Re: Re: Don't understand Plot behavior

  • To: mathgroup at smc.vnet.net
  • Subject: [mg40084] Re: [mg40071] Re: Don't understand Plot behavior
  • From: Dr Bob <drbob at bigfoot.com>
  • Date: Wed, 19 Mar 2003 03:22:58 -0500 (EST)
  • References: <b4pf6u$bu4$1@smc.vnet.net> <200303140945.EAA18797@smc.vnet.net> <b4ubb9$qkl$1@smc.vnet.net> <200303181050.FAA15646@smc.vnet.net>
  • Reply-to: drbob at bigfoot.com
  • Sender: owner-wri-mathgroup at wolfram.com

In this statement, Plot is wrapped around Evaluate, so Evaluate takes 
effect (regardless of what its argument might be -- what it is "wrapped 
around"):

Plot[Evaluate[{f[t],0}] , {t, 0, 1}]

In this statement, List is wrapped around Evaluate, so Evaluate doesn't 
take effect.  Again, it doesn't matter what Evaluate is wrapped around:

Plot[{Evaluate[f[t]],0} , {t, 0, 1}]

What matters is what is wrapped around Evaluate, not what Evaluate is 
wrapped around.

Bobby

On Tue, 18 Mar 2003 05:50:24 -0500 (EST), Jens-Peer Kuska 
<kuska at informatik.uni-leipzig.de> wrote:

> Hi,
>
> it has exactly to do with "where is Evaluate[] wrapped around"
>
> Because it does not appear "directly as the head of the function
> argument"
>
> Regards
> Jens
>
> Dr Bob wrote:
>>
>> It has nothing to do with what Evaluate is wrapped around.  From Help:
>>
>> "Evaluate only overrides HoldFirst, etc. attributes when it appears
>> directly as the head of the function argument that would otherwise be
>> held."
>>
>> Plot has attribute HoldAll, and List does not.
>>
>> Bobby
>>
>> On Fri, 14 Mar 2003 04:45:35 -0500 (EST), Jens-Peer Kuska
>> <kuska at informatik.uni-leipzig.de> wrote:
>>
>> > Hi,
>> >
>> > yes because Evaluate[] work only if it is
>> > waraped arround a function argument or a
>> > sequence of arguments, and you have to write
>> >
>> > Plot[Evaluate[{f[t],0}] , {t, 0, 1}]
>> >
>> > otherwise the List[] argument is evaluatet that
>> > help Plot[] nothing.
>> >
>> > Regards
>> > Jens
>
>



-- 
majort at cox-internet.com
Bobby R. Treat



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