[mathcad] RE: Sinus regression using genfit

[mathcad] RE: Sinus regression using genfit
Author: Potter, Mick Posted: Thu, 16 Feb 2006 11:21:30 -0000
Hi, My guess is that, without good initial guesses, this could be difficult to solve with any method. The most sensitive parameter is a1, which determines the frequency. I'm sure there are a large number of high frequency sine waves that would pass through or close to all the points (remember the textbook pictures of undersampled sine waves?). I attach a file (ver 11.2a) that analyses the data to get reasonable first guesses, and then uses Minerr to find a solution, although I'm sure Genfit or any other technique should be OK given these values. HTH == Mick \|From: Torgrim Sandvoll "mailto:torgrim" \|Sent: 15 February 2006 17:14 \|To: Mathcad Discussion List \|Subject: [mathcad] Sinus regression using genfit \| \|Hi, \| \|Trying to fit data to the general (sinusoidal) function: \|f(x,a):a0sin(a1(x+a2))+a3 \|(The periodic data for regression is often used in Norwegian highschool \|math) \| \|(See attached Mathcad (v11+) document) \| \|Have tried with genfit, but this method seems very sensitive to the guess \|values given. \| \|Any better way to solve this problem would be appreciated! \| \|Have a nice day! :-) \| \|Best regards, \|Torgrim Sandvoll \| \| \|______________________________________________________________________ \|This email has been scanned by the MessageLabs Email Security System. \|For more information please visit http://www.messagelabs.com/email \|______________________________________________________________________
Attachments: SINUSregresjon 2.mcd

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