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>