Re: Re: How to find which variable caused the trigger in Manipulate[]

*To*: mathgroup at smc.vnet.net*Subject*: [mg103879] Re: [mg103821] Re: How to find which variable caused the trigger in Manipulate[]*From*: John Fultz <jfultz at wolfram.com>*Date*: Sat, 10 Oct 2009 07:09:45 -0400 (EDT)*Reply-to*: jfultz at wolfram.com

This is a very simple version of what you asked for that doesn't solve some of the fundamental problems you'll probably come across, but it shows you the techniques to solving them. Principally... * Contain all evaluation inside of scoped Dynamics to prevent the entire Manipulate from refreshing. * Add flag variables (and perhaps you'll want other variables, too) as control variables, but with ControlType->None so they don't appear. * Use separate Dynamics, which display inside a Row[] as empty strings (this is important...remember that if a Dynamic doesn't display onscreen, then there's nothing available to update...see my previous posts on Dynamic if you're at all confused about this), to track the individual variables. + These separate Dynamics each scope a single variable only. + The scoped variable is determined by using Refresh with TrackedSymbols One of the problems my version doesn't solve is sensibly setting a start condition, so the evaluation assumes that the initial state has changed the y parameter (as a result of the initial creation of the flag-tracking dynamics). That's a problem I'll let you figure out. Manipulate[Row[{ Dynamic[ Refresh[xFlag = True; yFlag = False; "", TrackedSymbols -> {x}]], Dynamic[ Refresh[xFlag = False; yFlag = True; "", TrackedSymbols -> {y}]], Dynamic[ Text[StringJoin["you moved the ", Which[xFlag, "x", yFlag, "y"], " slider"]]] }], {x, 0, 1}, {y, 0, 1}, {{xFlag, False}, ControlType -> None}, {{yFlag, False}, ControlType -> None}] Sincerely, John Fultz jfultz at wolfram.com User Interface Group Wolfram Research, Inc. On Thu, 8 Oct 2009 07:49:43 -0400 (EDT), Nasser Abbasi wrote: > > > "Nasser Abbasi" <nma at 12000.org> wrote in message > news:hafbgr$j4r$1 at smc.vnet.net... > >>> Again, I want something like this >>> >>> Manipulate[ >>> process[( pickTheCorrectControlVariableWhichChanged ], >>> {a, 0, 1}, {b, 0, 1}, Initialization :> >>> >>> (process[arg_] := Module[{}, Plot[Sin[arg*x], {x, -Pi, Pi}]]) >>> ] >>> > >> I made some progress and I think I have a solution. >> >> I save the old value of each control variable in a global variable, then >> in >> the Manipulate expression, I check, using an If statement which current >> value of the control variable is different from the old value. I got it >> to >> work ok finally. >> >> Here is an example: >> >> olda = 999; >> oldb = 999; >> >> Manipulate[ >> If[olda != a, {olda = a; Style[StringJoin["a=", ToString[a]]]}, >> >> If[oldb != b, {oldb = b; Style[StringJoin["b=", ToString[b]]]}, >> >> Text["this message should NOT show up!"]]], {a, 0, 1}, {b, 0, 1}, >> >> LocalizeVariables -> True, TrackedSymbols -> {a, b}] >> >> > It is me again, with the same problem. > > I found out that I can NOT use global variables in a demo, and I also > can't > wrap the whole Manipulate inside a module. Any one of the above method > will > have solved this problem, but rules are rules, so now I have to find > another > solution. So I am stuck again. > > Before I recode everything again, which I would hate to do, I thought= I'll > ask one more time, may be some expert can have a solution. But this one= is > really hard. > > I'll explain again the problem to make sure we are all clear on it. > > I need to write a Manipulate where inside the Manipulate I need to detect > which slider or in other words, which control variable was changed. i.e. > which slider the user just changed to cause the Manipulate expression to > be > generated. (I need to do this so I can do different processing based on > the > slider that was selected) > > We all know that Manipulate generates a new version of its expression= when > one of the control variables changes value. I need to know which control > variable changed. > > There is the general layout > > Manipulate[ > > (* expression that uses control variables *) > > , > > (* controls here which update the control variables values *) > ] > > But there are restriction on the solution, since this will be for a demo. > Again, there can NOT be global variables used, (i.e. no variables in the > Manipulate initialization section, since these are global), and there can > NOT be a module around Manipulate[], i.e. no Module[{...}, > Manipulate[...]] > allowed. > > Here is a small code to show the problem > > Manipulate[ > Text[StringJoin["you moved the ", "x or y", " slider"]], > {x, 0, 1}, > {y, 0, 1} > ] > > Could someone modify the above, so that the code above will tell which > slider the user _just_ moved? > > It seems like an impossible problem for me to solve without the use of > global variables or a module around Manipulate. > > Here is what I tried so far, and this fail: > > Manipulate[ > Which[ > > x != oldx, > {oldx = x; Text[StringJoin["you moved the ", "x ", " slider"]]}, > > y != oldy, > {oldy = y; Text[StringJoin["you moved the ", "y ", " slider"]]}, > > True, Text["why Ami here??"] > ], > > {x, 0, 1}, > {y, 0, 1}, > {oldx, -999, ControlType -> None}, > {oldy, -999, ControlType -> None} > ] > > The reason it fail is because oldx and oldy are updated to the same value > of > x and y whenever x or y changes before I get the chance to do the > comparison. I.e. when the new version of the expression is generated, > oldx=x > and oldy=y each time. This seems to consequences of Manipulate= generating > DynamicModule[] for the whole thing. You can see this by using the > SnapShot > option on the Manipulate output. This will generate the whole expression > form. (Nice tool). > > If someone can make it so that the above will display the correct message > each time, then I would declare that person to be the Mathematica Guru of > the year. > > I think I have reached the limit of my current Mathematica understanding > when it comes to internals of Manipulate and Dynamics to be to solve this > one. But I'll keep on looking. > > Thank you, > --Nasser

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