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Fitting step function

• To: mathgroup at smc.vnet.net
• Subject: [mg122079] Fitting step function
• From: premiumxy <spam at stefanabel.com>
• Date: Wed, 12 Oct 2011 03:44:07 -0400 (EDT)
• Delivered-to: l-mathgroup@mail-archive0.wolfram.com

Hello,

I have the following problem: I have a set of data about some phase information of a signal. At certain points there is a clear step of 180 degrees.

I would like to fit this data to find the x-coordinates of these steps. I have the feeling that "normal" step-functions in Mathematica (such as UnitStep, HeavisideTheta, Sign...) are not varied in the fit-routines (such as NonlinearModelFit). I guess it this is caused by the functions not being continuous.

I would appreciate any hints for this quite simple (?)problem. The only option that I can currently see is to create a "step-like" continuous function such as Tanh[A x] (with A>>1)

Thanks!

• Follow-Ups:
  • Re: Fitting step function
    • From: Barrie Stokes <Barrie.Stokes@newcastle.edu.au>
  • Re: Fitting step function
    • From: Jacopo Bertolotti <jacopo.bertolotti@gmail.com>
  • Re: Fitting step function
    • From: Virgil Stokes <vs@it.uu.se>