How show Locator point and its image under a function?

*To*: mathgroup at smc.vnet.net*Subject*: [mg79866] How show Locator point and its image under a function?*From*: Murray Eisenberg <murray at math.umass.edu>*Date*: Tue, 7 Aug 2007 01:32:24 -0400 (EDT)*Organization*: Mathematics & Statistics, Univ. of Mass./Amherst*Reply-to*: murray at math.umass.edu

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 Eisenberg murray 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

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