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Re: Using Locators in Mathematica v6

  • To: mathgroup at
  • Subject: [mg76472] Re: Using Locators in Mathematica v6
  • From: Jens-Peer Kuska <kuska at>
  • Date: Wed, 23 May 2007 05:07:04 -0400 (EDT)
  • Organization: Uni Leipzig
  • References: <f2u4tq$jv5$>
  • Reply-to: kuska at


what is with
data = Table[{x, 1 + 2*x + 0.5*Random[]}, {x, -2, 2, 0.2}];

  DynamicModule[{points, dfit, plt},
   points = Append[data, pnt];
   dfit = Fit[points, {1, x}, x];
   Plot[dfit, {x, -2, 2}, Evaluated -> True ,
    Epilog -> {Point /@ data}]
   ], {{pnt, {0, 0}}, Locator}]


Coleman, Mark wrote:
> Greetings,
> I've been exploring some of the new dynamic interface elements in Mathematica v6
> and I must say they are very impressive indeed. I've managed to set-up
> some useful examples using Manipulate. Unfortunately the documentation
> of
> One example I am working on involves the use of Locators. The example
> itself seem straightforward but I cannot quite get the effect I am
> looking for.  I am hoping someone on MathGroup can point me in the right
> direction.
> Briefly, I want to illustrate the effects that outlier points an have on
> a line of best fit. For my example, I generate a small random set of
> points (x(i), y(i)), where y(i) = a + b x(i) + randomerror(i), for
> values a and b. I then calculate the line of best fit using Fit[ ]. I
> next ListPlot[ ] the underlying set of points and overlay the resulting
> line from Fit[ ]. So far very simple.
> In my dynamic example, I'd like to have a locator button appear on the
> graph such that the (x,y) location of the locator becomes an additional
> data point in the overall data set, and thereafter a new line of best
> fit is calcuated and displayed. Thus as the user moves the locator, a
> new best fit line is displayed.
> I'd appreciate any assistance other readers might offer.
> Thanks,
> -Mark

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