       Re: Can a Locator be Made to Track a Curve?

```Try this slightly modified version and  see what happens for  0<x< 1

locator =   Graphics[{Red, Disk[{0, 0}, Offset], Black,  Circle[{0, 0},
Offset], Circle[{0, 0}, Offset] },   ImageSize -> 30];

f[x_] := Sin[x] E^-x;
g[{x_, _}] := {x, f@x}
pt = {0, 0};
LocatorPane[Dynamic[pt, (pt = g@#) &], Plot[f[x], {x, 0, 2 Pi}],  Appearance
-> locator]

The locator tends to go out of control  for 0<x< 1.  I observed this, say,
abnormal  behavior for all versions posted;  after changing f[x_] := Sin[x]
to   f[x_] := Sin[x] E^-x. It seems the problem is not related to the
inclusion of the tailored locator (works the same for the built in one).
Sometimes the locator tends to jump or get stuck within 0<x< 1 range.

-----Mensaje original-----
De: DrMajorBob [mailto:btreat1 at austin.rr.com]
Enviado el: lunes, 08 de agosto de 2011 10:21
Para: mathgroup at smc.vnet.net
Asunto: Re: Can a Locator be Made to Track a Curve?

A bit simpler, I think, is:

f[x_] := Sin[x];
g[{x_, _}] := {x, f@x}
pt = {0, 0};
LocatorPane[Dynamic[pt, (pt = g@#) &], Plot[Sin[x], {x, 0, 2 Pi}]]

Bobby

On Sun, 07 Aug 2011 05:14:52 -0500, Heike Gramberg
<heike.gramberg at gmail.com> wrote:

> You could do something like
>
> f[x_] := Sin[x];
> pt = {0, 0};
> LocatorPane[Dynamic[pt, (pt[] = #[]; pt[] = f[#[]]) &],
> Plot[Sin[x], {x, 0, 2 Pi}]]
>
> Heike
>
> On 6 Aug 2011, at 08:12, Gregory Lypny wrote:
>
>> Hello everyone,
>>
>> Can a locator be constrained so that it tracks a curve?
>>
>> Regards,
>>
>> Gregory
>>
>
>

--
DrMajorBob at yahoo.com

```

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