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

  • To: mathgroup at
  • Subject: [mg120752] Re: Can a Locator be Made to Track a Curve?
  • From: DrMajorBob <btreat1 at>
  • Date: Tue, 9 Aug 2011 07:18:16 -0400 (EDT)
  • Delivered-to:
  • References: <> <j1loki$nlf$>
  • Reply-to: drmajorbob at

Clearly, it is easier with top-posting to see the most recent response.

In a deep thread where this might be a tenth-level response and each  
response can be long, it is heinous (IMHO) having to scroll down, staring  
at messy text with up to ten ">" characters before each line, with hideous  
line-wrapping in places, searching for new material at the very bottom.  
I'd rather scroll down only far enough to get the gist of things or find  
the newest thing I haven't already seen.

Worse is a mix of top-posters and bottom-posters, wherein it's well-nigh  
impossible to decipher what the sequence was.

Worst of all is a mix of top-posters, bottom-posters, and those who use  
threaded newsreaders, who do not include what came before AT ALL, hence  
giving no clue (to the rest of us) what the hell they're talking about.


On Mon, 08 Aug 2011 03:20:23 -0500, Helen Read <readhpr at> wrote:

> You might like to add a PlotLabel showing the coordinates.
> f[x_] := Sin[x];
> pt = {0, 0};
> LocatorPane[Dynamic[pt, (pt[[1]] = #[[1]]; pt[[2]] = f[#[[1]]]) &],
>   Plot[Sin[x], {x, 0, 2 Pi}, PlotLabel -> Dynamic[pt]]]
> P.S. -- Grumpy OT Aside: When did everyone in the world become
> top-posters? I'm finding it everywhere...newsgroups, email from family,
> friends, co-workers, basically everyone. For years I used to rearrange
> it back to traditional bottom-posting when replying to something that
> was top-posted, but top-posting has become so prevalent that I have
> given up. Did I miss the memo that top-posting is now preferred?
> On 8/7/2011 6:15 AM, Heike Gramberg wrote:
>> You could do something like
>> f[x_] := Sin[x];
>> pt = {0, 0};
>> LocatorPane[Dynamic[pt, (pt[[1]] = #[[1]]; pt[[2]] = f[#[[1]]])&],
>> 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

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