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Bug in Manipulate with Trigger control?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg92750] Bug in Manipulate with Trigger control?
  • From: "michael.p.croucher at googlemail.com" <michael.p.croucher at googlemail.com>
  • Date: Sun, 12 Oct 2008 04:32:43 -0400 (EDT)

Hi all

I have been playing around with Manipulate a bit and am wondering
about the behavior of the code below

Manipulate[
 theta = pointnum*2 Pi/128.;
 x = r Cos[theta];
 y = r Sin[theta];
 Pointlist[[pointnum]] = Point[{x, y}];
 Graphics[{PointSize[Large],
   Point[{x, y}], {PointSize[Small], Pointlist}},
  PlotRange -> {{-5, 5}, {-5, 5}}]
 , {r, 2, 4}
 , {pointnum, 1, 129, 1, ControlType -> Trigger,
  DisplayAllSteps -> True, AnimationRepetitions -> 10}
 , TrackedSymbols -> {pointnum, r},
 Initialization :> {Pointlist = Table[{}, {129}]}
 ]

When the pointnum trigger is pressed a big point traces a circle and
leaves a trail of smaller points behind it.  In my current setup
(6.0.0 on windows) the trail is sometimes incomplete despite the fact
that I have asked for DisplayAllSteps->True

The code above always seems to misses the 78th point on my machine.
Does anyone know what is going on?

Finally, AnimationRate doesn't work as expected.  Putting
AnimationRate->64 should take 2 seconds for a complete circle but it
takes longer.

It's 2am so maybe I am just being dense and everything is behaving as
it should be...another pair of eyes would be greatly appreciated.

Cheers,
Mike


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