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Re: Dynamic, UpdateInterval and global variable

  • To: mathgroup at smc.vnet.net
  • Subject: [mg95650] Re: Dynamic, UpdateInterval and global variable
  • From: dh <dh at metrohm.com>
  • Date: Sat, 24 Jan 2009 06:16:49 -0500 (EST)
  • References: <gl4a43$ge6$1@smc.vnet.net>


Hallo Antoine,

I guess what is happening is that Mathematica tries every second to make a full 

update. But because the value of aDisk is changeing all the time, it 

will never finish the first update.

To slow down this, you may delete Refresh and put a "Pause" statement 

instead:

Dynamic[pt = pt + RandomReal[{0, 0.2}, 2]; Pause[1]; aDisk[pt]]



hope this helps, Daniel



Antoine wrote:

> Hello everybody,

> 

> 

> With Mathematica, I would like to have a Disk which "evades" from the origin in a Dynamic, 

> with an UpdateInterval of 1 second.

> 

> 

> To fix the ideas the function

> 

> 

> aDisk[{x_, y_}] := 

>  Graphics[Disk[{x, y}, 0.2], PlotRange -> {{-2, 2}, {-2, 2}}, 

>   Axes -> True, AxesStyle -> RGBColor[0.47451, 0.482353, 0.47451]]

> 

> 

> will draw in disk of center {x,y}, radius 0.2, in a fixed PlotRange.

> Everything is fine.

> 

> 

> The following code:

> 

> 

> ListAnimate[

>  Map[aDisk, NestList[# + RandomReal[{0, 0.2}, 2] &, {0., 0.}, 10]]]

> 

> 

> does what I want in a ListAnimate.

> 

> 

> I would like the same in a Dynamic instruction.  In the following lines

> the problem is the global variable pt.  It seems that the option UdpdateInterval

> is not "respected" when a global variable is used:

> 

> 

> pt = {0, 0};

> Dynamic[Refresh[pt = pt + RandomReal[{0, 0.2}, 2]; aDisk[pt], 

>   UpdateInterval -> 1]]

> 

> 

> Mathematica does not "wait" a second.  The Disk evades quickly ...

> 

> 

> What should I write to see the disk going slowly up-right in a Dynamic ?

> I have tried with Module, DynamicModule, but nothing worked out.

> 

> 

> Thank you very much for your help.

> 

> 

> Antoine.

> 




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