Re: Non Linear fit problem
- To: mathgroup at smc.vnet.net
- Subject: [mg67868] Re: Non Linear fit problem
- From: dh <dh at metrohm.ch>
- Date: Tue, 11 Jul 2006 05:58:33 -0400 (EDT)
- References: <e8nst3$k60$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Hi Raj, I am not sure that I understand what you are saying. You have 2 time series whose amplitudes are proportional with a factor Erf[..] but whose time behaviour have a shift? The shift is best computed using Correlation. If you know the shift, you can then shift one of the series and fit the factor. Daniel Raj wrote: > I have a problem of fitting two temperature lists to an error > function. The physical description of the problem is as follows: > > t1 is a list of temperatures on the surface of the soil and t2 is the > list of temperatures at a certain depth (say x). > We know that the dependence of t2 on t1 is as > > t2 = t1 Erfc[x/(2 sqrt(k)] > > where x is the depth at which t2 is measured and k is the constant of > diffusivity. > > When I plot the two temperatures, I can see that t2(temperature at a > depth) lags behind t1 by a certain time. > My problem is to find the temperature at any depth given the > temperature at the surface (t1). Is there a way in Mathematica to find > k such that t2 and t1 have a close fit? > > > Thanks, > > Raj >