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Re: Follow-Up Question to

  • To: mathgroup at
  • Subject: [mg20204] Re: [mg20187] Follow-Up Question to [mg20090]
  • From: "Andrzej Kozlowski" <andrzej at>
  • Date: Wed, 6 Oct 1999 21:06:25 -0400
  • Sender: owner-wri-mathgroup at

But this is simply not true:

disp = DisplayFunction -> Identity;
ClearAttributes[Plot, HoldAll]
SetAttributes[Plot, HoldFirst]
Plot[x^3, {x, -1, 1}, disp]

No picture. You must have done something different.
Andrzej Kozlowski
Toyama International University

>From: hanssen at
To: mathgroup at
>To: mathgroup at
>Subject: [mg20204] [mg20187] Follow-Up Question to [mg20090]
>Date: Tue, Oct 5, 1999, 17:04

> Hi, all
> Adam Smith rose the question, why  nodisp in
> nodisp = DisplayFunction -> Identity
> graph1 = Plot[Sin[2 Pi x],{x,0,2},nodisp]
> does not work. From the answers in this group, we learned,
> that one either has to wrap nodisp into Evaluate
> graph1 = Plot[Sin[2 Pi x],{x,0,2},Evaluate[nodisp]]
> or use Block to temporarily deviate DisplayFunction to Identity
> and use Show outside the Block-construct to display the combined
> graphs or use one or the other package to combine different graphs.
> Plot has the Attribute HoldAll. However, if one changes this
> to HoldFirst (which might have other unwanted side effects),
> Evaluate around nodisp is still necessary. Can anybody in this
> group explain, why? It is just a matter of better understanding
> Hold and so on, rather than a question of combining graphics
> objects.
> sincerely
> A. Hanszen

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