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Re: unwrap modulo 2pi [message #23640 is a reply to message #23639]

Wed, 07 February 2001 10:48

Dave Greenwood
Messages: 33
Registered: October 2000

Member

I wrote:
> graham_wilson@my-deja.com wrote:
>> My appologies for not being explicit enough...
>>
>> 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?
>
> Surely I must be missing something(?):
>
> IDL> print, c + fix(a/b)*b
> 2.00000 4.00000 6.00000 8.00000 10.0000 12.0000

And a proverbial ohnosecond later I went - "Oh No!". I guess I better
go back to lurking. ;-(

Btw, given that (a mod b) = (a+(n*b) mod b) do you expect your 'unwraping'
function to give the lowest value of a such that c = a mod b?

Dave

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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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