Services & Resources / Wolfram Forums
MathGroup Archive
*Archive Index
*Ask about this page
*Print this page
*Give us feedback
*Sign up for the Wolfram Insider

MathGroup Archive 1999

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: searching for an enveloppe

  • To: mathgroup at
  • Subject: [mg15728] Re: searching for an enveloppe
  • From: Daniel Lichtblau <danl>
  • Date: Fri, 5 Feb 1999 03:42:23 -0500 (EST)
  • Organization: Wolfram Research, Inc.
  • References: <78ui46$>
  • Sender: owner-wri-mathgroup at

Olivier Leroy wrote:
> I'd like to know the envelope of a curve. The data come from image
> processing, and are known as a list of points, function of distance.
> Does a method already exist to have an upper envelope near by the curve
> ?
> Juliette Marais
> ___________________
> France.

If your data points are not misbehaving too badly the following approach
might be useful. Assume the curve is approximated by a low degree
polynomial of the form p(x,y)=0.

(i) Find a least-squares fit to obtain coefficients for p(x,y). (ii) Get
an envelope by allowing a small offset, say |p(x,y)|<=epsilon.

Daniel Lichtblau
Wolfram Research

  • Prev by Date: InterpolatingFunction
  • Next by Date: Displaying the intermediate steps of an evaluation
  • Previous by thread: Re: interpolatingfunction
  • Next by thread: Displaying the intermediate steps of an evaluation