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MathGroup Archive 2007

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Re: forming continuous "trail" with Locator

  • To: mathgroup at smc.vnet.net
  • Subject: [mg79919] Re: forming continuous "trail" with Locator
  • From: markholtuk at googlemail.com
  • Date: Thu, 9 Aug 2007 05:09:34 -0400 (EDT)
  • References: <f96jsd$qh3$1@smc.vnet.net><f990nd$c0s$1@smc.vnet.net>

Aah, I see. Thanks Mariusz.

So what I should have done is more like this then?:

list = {};
Manipulate[AppendTo[list, pnt]; FinishDynamic[];
 LocatorPane[Dynamic[pnt],
  Graphics[{{Gray, Disk[{32, 32}, 32]},
    Dynamic[{Hue[0], Point /@ (DeleteCases[list, Null])}]}]], {pnt}]

Mark

On Aug 8, 10:14 am, Mariusz Jankowski <mjankow... at usm.maine.edu>
wrote:
> Mark, you made the first argument of Manipulate a list, the three
> elements are AppendTo, LocatorPane, and FinishDynamic. You suppressed
> the output of the first and the output of the third is Null - which is
> exactly what you see in the Manipulate panel.
>
> Bye, Mariusz
>
> markhol... at googlemail.com wrote:
> > Hi Murray,
> > Does this do what you want?:
>
> > list = {};
> > Manipulate[{AppendTo[list, pnt];
> >   LocatorPane[
> >    Dynamic[pnt], {Graphics[{{Gray, Disk[{32, 32}, 32]},
> >       Dynamic[{Hue[0], Point /@ DeleteCases[list, Null]}]}]}],
> >   FinishDynamic[]}, {pnt}]
>
> > - sorry about the Null next to the graphic - not sure why it's there!
>
> > To plot the trace afterwards:
>
> > ListPlot[DeleteCases[list, Null], Joined -> True, PlotRange -> All,
> >  AspectRatio -> Automatic]
>
> > On Aug 6, 8:50 am, Murray Eisenberg <mur... at math.umass.edu> wrote:
> >> Is there some way in Mathematica 6 to use a Locator so as to create a
> >> continuous-appearing "trail" after you click and then drag the cursor
> >> around?
>
> >> Of course one could write code allowing addition of points through
> >> successive clicks, and then one could try to click repeatedly on
> >> successive points very near one another, but that could get very tedious.
>
> >> I mean the sort of thing one gets in drawing programs (and with the
> >> Mathematica 6 2D Drawing Tools).
>
> >> --
> >> Murray Eisenberg                     mur... at math.umass.edu
> >> Mathematics & Statistics Dept.
> >> Lederle Graduate Research Tower      phone 413 549-1020 (H)
> >> University of Massachusetts                413 545-2859 (W)
> >> 710 North Pleasant Street            fax   413 545-1801
> >> Amherst, MA 01003-9305
>
> > Best wishes,
>
> > Mark
> > ___________________
> > Mark R. Holt, BA, PhD
> > Cardiovascular Division and
> > Randall Division of Cell and Molecular Biophysics
> > New Hunt's House
> > King's College London
> > Guy's Hospital Campus
> > LONDON, U.K., SE1 1UL
> > Phone: +44 20 7848 6438
> > Fax:     +44 20 7848 6435




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