Re: Fitting step function
- To: mathgroup at smc.vnet.net
- Subject: [mg122124] Re: Fitting step function
- From: premiumxy <spam at stefanabel.com>
- Date: Sat, 15 Oct 2011 06:04:05 -0400 (EDT)
- Delivered-to: l-mathgroup@mail-archive0.wolfram.com
Thanks for your quick and very useful replies!
@Jacopo:
Actually, I already started to follow the approach that you mentioned. The main problem is that my data is at some points quite noisy, and I often have single points that are far off.
To not identify these points with your approach, I would have to filter them out/average the rest... it works, but is not as nice compared to a real fitting procedure, to my opinion.
@Barrie:
I did not fully understand your message: I see that you used a ArcTan function to fit the data. Similar to a Tanh function, this is a continuous function where I did not really encounter any problems.
A main question for me was: why do the step-functions (like UnionStep...) not work with the fitting routine (at least in my case, it did not vary the parameters during the NonlinearModel fit.
Could you also use a step function in your example?
Also, since you asked, here is a typical dataset. There are phase steps, one at x=0 (Degrees), and the other one at approx x=-70. Please let me know if you need further infos. (The x-values correspond to angles, and do to symmetry considerations the data should be identical for x=+/-180 (Degree) shifts).
Thanks!
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