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Tracking point on a plot

• To: mathgroup at smc.vnet.net
• Subject: [mg76929] Tracking point on a plot
• From: Murray Eisenberg <murray at math.umass.edu>
• Date: Wed, 30 May 2007 05:20:39 -0400 (EDT)

I want a locator on the plot of, say, Sin[x], that will move only
along the graph of the function.  How should this be done?

The closest I've come so far is the following, where the x-coordinate
is being read from wherever the mouse is, but the corresponding
{x,Sin[x]} point on the curve is where the locator appears:

  DynamicModule[{p=0},
    LocatorPane[{Dynamic[p],Dynamic[Sin[p]]},
         Plot[Sin[x],{x,0,10}]
       ]
    ]

(Also, onece the expression is evaluated, each time I move the mouse I
get a Set::write message about Tag Sin in Sin[...] being protected.)

-- 
  Murray Eisenberg                       Internet:  murray at math.umass.edu
  Mathematics & Statistics Dept.            Voice:  413-545-2859 (W)
  University of Massachusetts                       413-549-1020 (H)
  Amherst, MA 01003                           Fax:  413-545-1801

• Follow-Ups:
  • Re: Tracking point on a plot
    • From: Chris Hill <chill@wolfram.com>