Re: How show Locator point and its image under a function?

*To*: mathgroup at smc.vnet.net*Subject*: [mg79905] Re: How show Locator point and its image under a function?*From*: David Bailey <dave at Remove_Thisdbailey.co.uk>*Date*: Wed, 8 Aug 2007 04:56:14 -0400 (EDT)*References*: <f990t4$c2d$1@smc.vnet.net>

Murray Eisenberg wrote: > The following code displays a fixed point and its image under a > specified function f: > > f[{x_,y_}]:={2x+1,y+2} > Module[{pt = {-1, 0.5}}, > Row[{ > Framed@Graphics[Point[pt], PlotRange -> 5], > Framed@Graphics[Point[f[pt]], PlotRange -> 5] > }] > ] > > Now I want to have the point in the left-hand graphic to be dynamic, > controlled by a Locator, and to have its changed image under the > function to be shown in the right-hand graphic. > > The idea is something like the following (WRONG!) code: > > DynamicModule[{pts={{0,0}}}, > Row[{ > LocatorPane[Dynamic[pts],Graphics[{},PlotRange->5]], > Graphics[Dynamic[f/@pts],PlotRange->5] > }] > ] > > That code produces error messages, "1 is not a Graphics primitive or > directive", "2 is not a Graphics primitive or directive". > > How can it actually be done? > Murray, You forgot to make Point objects in your Graphics! DynamicModule[{pts = {{0, 0}}}, Row[{LocatorPane[Dynamic[pts], Graphics[{}, PlotRange -> 5]], Graphics[Dynamic[Point /@ f /@ pts], PlotRange -> 5]}]] David Bailey http://www.dbaileyconsultancy.co.uk

**Follow-Ups**:**Re: Re: How show Locator point and its image under a function?***From:*Murray Eisenberg <murray@math.umass.edu>