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Re: unwrap modulo 2pi [message #23723 is a reply to message #23642]

Thu, 08 February 2001 01:13

Wim Bouwman
Messages: 8
Registered: September 1997

Junior Member

In the following bit of code the measured phase P is unwrapped onto
CALCPhi.
This is done by doing a 2nd order extrapolation of the three previous
points. It works when the jumps are not too extreme.

;Correct Phi and PhiOne for 2Pi jumps. The calculated Phi is compared to
;the experimentally obtained Phi. Extrapolation with least squares fit.
NPhi=N_ELEMENTS(P)
CALCphi=DBLARR(NPhi)
FOR i=3,(NPhi-1) DO BEGIN
CALCphi(i)=(-2*P(i-3)+P(i-2)+4*P(i-1))/3
Njumps=NINT((CALCphi(i)-P(i))/(2*!DPi), /Long)
P(i)=P(i)+Njumps*2*!DPi
ENDFOR

graham_wilson@my-deja.com wrote:

> IDL> a=[2,4,6,8,10,12]
> IDL> a=[2.,4.,6.,8.,10.,12.]
> IDL> b=2*!PI
> IDL> c=a mod b
> IDL> print, c
> 2.00000 4.00000 6.00000 1.71681 3.71681 5.71681
>
> What I mean by 'unwraping' is: Given I know 'c' and 'b' how do I
> explicitly find a?

--

Dr. Wim G. Bouwman phone (++31) (0)15 2786775
Interfacultair Reactor Instituut fax (++31) (0)15 2788303
Technische universiteit Delft w.g.bouwman@iri.tudelft.nl
Mekelweg 15 http://www.iri.tudelft.nl/~bouwman
2629 JB Delft The Netherlands

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[Message index]

		Re: unwrap modulo 2pi By: Pavel A. Romashkin on Wed, 07 February 2001 15:25
		Re: unwrap modulo 2pi By: Craig Markwardt on Wed, 07 February 2001 13:07
		Re: unwrap modulo 2pi By: Pavel A. Romashkin on Wed, 07 February 2001 12:39
		Re: unwrap modulo 2pi By: Randall Skelton on Wed, 07 February 2001 11:48
		Re: unwrap modulo 2pi By: tam on Wed, 07 February 2001 11:18
		Re: unwrap modulo 2pi By: Dave Greenwood on Wed, 07 February 2001 10:48
		Re: unwrap modulo 2pi By: Dave Greenwood on Wed, 07 February 2001 10:29
		Re: unwrap modulo 2pi By: graham_wilson on Wed, 07 February 2001 09:52
		Re: unwrap modulo 2pi By: Pavel A. Romashkin on Wed, 07 February 2001 09:02
		Re: unwrap modulo 2pi By: graham_wilson on Wed, 07 February 2001 07:30
		Re: unwrap modulo 2pi By: Wim Bouwman on Fri, 09 February 2001 00:42
		Re: unwrap modulo 2pi By: Craig Markwardt on Thu, 08 February 2001 07:43
		Re: unwrap modulo 2pi By: Wim Bouwman on Thu, 08 February 2001 01:13

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