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Follow-Up Question to

  • To: mathgroup at smc.vnet.net
  • Subject: [mg20187] Follow-Up Question to [mg20090]
  • From: hanssen at zeiss.de
  • Date: Tue, 5 Oct 1999 04:04:17 -0400
  • Sender: owner-wri-mathgroup at wolfram.com

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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