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Re: Speaking of curve fitting... [message #58470 is a reply to message #58469]

Thu, 31 January 2008 08:17

Paul Van Delst[1]
Messages: 1157
Registered: April 2002

Senior Member

Lasse Clausen wrote:
> ... run the following code, spot the difference and explain, s'il vous
> plait.
>
> nn = 1000
> xx1 = dindgen(nn)
> xx2 = timegen(nn, start=julday(5,25,1980,11,23))
>
> yy1 = sin(2.*2.*!pi*xx1/(nn-1.))
>
> d = poly_fit(xx1, yy1, 6, yfit=yfit1, /double)
> d = poly_fit(xx2, yy1, 6, yfit=yfit2, /double)

Try
d = poly_fit(xx2-xx2[0], yy1, 6, yfit=yfit2, /double)

>
> !p.multi = [0,1,2]
> plot, xx1, yy1, /xstyle
> oplot, xx1, yfit1, linestyle=1
> plot, xx2, yy1,/xstyle
> oplot, xx2, yfit2, linestyle=1
>
> end
>
> I had a quick look at POLY_FIT.PRO but I can spot nothing which could
> explain the above behaviour. I run 32bit IDL 6.4 on some Linux.
>
> Cheers
> Lasse Clausen

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[Message index]

		Re: Speaking of curve fitting... By: David Fanning on Thu, 31 January 2008 09:13
		Re: Speaking of curve fitting... By: Paul Van Delst[1] on Thu, 31 January 2008 09:04
		Re: Speaking of curve fitting... By: Vince Hradil on Thu, 31 January 2008 08:42
		Re: Speaking of curve fitting... By: pgrigis on Thu, 31 January 2008 08:34
		Re: Speaking of curve fitting... By: lasse on Thu, 31 January 2008 08:33
		Re: Speaking of curve fitting... By: Paul Van Delst[1] on Thu, 31 January 2008 08:17

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