Re: updating a simulation within Manipulate.

*To*: mathgroup at smc.vnet.net*Subject*: [mg130089] Re: updating a simulation within Manipulate.*From*: W Craig Carter <ccarter at MIT.EDU>*Date*: Fri, 8 Mar 2013 16:46:28 -0500 (EST)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*Delivered-to*: l-mathgroup@wolfram.com*Delivered-to*: mathgroup-newout@smc.vnet.net*Delivered-to*: mathgroup-newsend@smc.vnet.net*References*: <20130308035142.51AD66799@smc.vnet.net> <5139E091.8000909@idi.ntnu.no>

Thanks Waclwaw, That is informative; I'm going to have to read the docs about ScheduledTask[]s. My "real" example is quite a bit more involved---I have a Manipulate buried inside a Manipulate. I am not looking at random walks per se, but that was an example I cooked up which was simple enough to illustrate my question. I think this is the preferred method for asking questions in the group? (As long as one doesn't make the silly typos that I am prone to..). Thanks, Craig W Craig Carter Professor of Materials Science, MIT On Mar 8, 13, at 7:58 AM, Waclaw Kusnierczyk wrote: > Hi Craig, > > Looks like you want to dynamically show the progress of a random walk. Rather than directly modify your solution, I'd suggest to have a look at an alternative using scheduled tasks and buttons. > > An example of random walk code: > > step[bias_] := > Through[{Cos, Sin}[RandomVariate[NormalDistribution[bias, 1]]]] > next[state_, bias_] := > state + step[bias] > extend[path_, bias_] := > Append[path, next[Last@path, bias]] > > An example of random walk plot code: > > show[path_] := > Show[ > ListLinePlot[path, > PlotMarkers -> {Graphics[Circle[{0, 0}, 1]], 0.015}, > Axes -> None, > AspectRatio -> 1, > PlotRange -> {{-10, 10}, {-10, 10}}], > Graphics[{Red, Point[Last@path]}]] > > An example of dynamic random walk plot: > > Module[{path = {{0, 0}}, walk, bias = 0}, > Manipulate[ > show[path], > Column@{ > Row@{ > Button["start", Quiet@RemoveScheduledTask@walk; > walk = RunScheduledTask[path = extend[path, bias], 0.5]], > Button["stop", StopScheduledTask[walk]], > Button["reset", path = {{0, 0}}]}, > AngularGauge[Dynamic@bias, {-\[Pi], \[Pi]}, > ScaleOrigin -> {-\[Pi], \[Pi]}]}]] > > Best, > vQ > > > On 03/08/2013 04:51 AM, W Craig Carter wrote: >> >> I *think* I've asked this question before, but I can't find it on mathgroup. In any case, I don't know the answer now. >> >> Here is a simple example of a Manipulate that updates a graphic as long as a boolean is true. This method seems like a kludge to me---is it? If so, what would be a better way to do this. >> >> This is a constructed example, the real case I am looking at is much more involved; but kudos to anyone who can make a reasonable facsimile of their signature by adjusting the random walker's bias.... >> >> randomStep[bias_, stepList_] := >> Module[{angle = RandomVariate[NormalDistribution[bias, 1]]}, >> Join[stepList, {Last[stepList] + {Cos[angle], Sin[angle]}}]] >> >> walkerGraphic[stepList_, range_] := >> Graphics[GraphicsComplex[stepList, Disk /@ Range[Length[stepList]]], >> PlotRange -> range {{-1, 1}, {-1, 1}}] >> >> DynamicModule[ >> {walkerPath = {{0, 0}}}, >> Manipulate[ >> If[keepWalking, (* kludge warning---testing for If[True...] seems inefficient *) >> walkerPath = randomStep[bias, walkerPath] >> ]; >> If[reset, >> reset = False; keepWalking = False; >> walkerPath = {{0, 0}} >> ]; >> walkerGraphic[walkerPath, range], >> {{keepWalking, False}, {True, False}}, >> {{reset, False}, {True, False}}, >> Delimiter, >> {{range, 20}, 0, 100}, >> {{a, 0}, -Pi, Pi, >> AngularGauge[##, ImageSize -> 160 , >> ScaleOrigin -> {{-4 Pi, 4 Pi}, 1}] &} >> ] >> ] >> >> >> >> W Craig Carter >> Professor of Materials Science, MIT >

**References**:**updating a simulation within Manipulate.***From:*W Craig Carter <ccarter@MIT.EDU>