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MathGroup Archive 2004

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Re: Null entry in a Graphics list?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg51812] Re: [mg51795] Null entry in a Graphics list?
  • From: Andrzej Kozlowski <akoz at mimuw.edu.pl>
  • Date: Wed, 3 Nov 2004 01:23:24 -0500 (EST)
  • References: <200411020705.CAA21665@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

On 2 Nov 2004, at 16:05, AES/newspost wrote:

>
> Is there a "Null" or a "None" for Graphics?
>
> If I want to accomplish something like
>
>     g1 = Graphics[---];
>     g2 = Graphics[---]
>     g3 = If[test, Graphics[---], NoGraphics ];
>
>     Show[g1, g2, g3 ];
>
> is there something I can put in for "NoGraphics" (other than an
> offscreen Point or a zero-size Point or . . . ) that will be acceptable
> in subsequent graphics commands
>
>
The empty list {} should work. For example:

g1 = Plot[
   x^2, {x, -1, 1},
     DisplayFunction ->
       Identity];
  g2 = Plot[x^3, {x, -1, 1}, DisplayFunction -> Identity];

g3 := If[t, g1, {}]

t = True;

Show[g3, g2, DisplayFunction -> $DisplayFunction]

(two graphs)

t=False;

Show[g3,g2,DisplayFunction->$DisplayFunction]

(one graph)


Andrzej Kozlowski
Chiba, Japan
http://www.akikoz.net/~andrzej/
http://www.mimuw.edu.pl/~akoz/


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