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Re: finding the center of gravity of an irregularly shaped roi within a 2d array [message #81256 is a reply to message #81253]

Mon, 03 September 2012 09:26

David Fanning
Messages: 11724
Registered: August 2001

Senior Member

David Fanning writes:

>
> ian.j.ashpole@googlemail.com writes:
>
>> If i can ask, as i am unable to find this in the code as a relative novice, how does your program actually calculate the centroid coordinates?
>
> Each pixel in the ROI is assigned a "weight" of 1, then
> a simple center-of-mass calculation is done:
>
> totalMass = Total(array)
> xcm = Total( Total(array, 2) * Indgen(arrayXSize) * scale[0] ) $
> / totalMass
> ycm = Total( Total(array, 1) * Indgen(arrayYSize) * scale[1] ) $
> / totalMass
> center = [xcm, ycm]

Sorry, I meant to include a link to additional information about
center-of-mass calculations:

http://www.idlcoyote.com/tips/centroid.html

Cheers,

David

--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.idlcoyote.com/
Sepore ma de ni thui. ("Perhaps thou speakest truth.")

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[Message index]

		Re: finding the center of gravity of an irregularly shaped roi within a 2d array By: ian.j.ashpole on Tue, 04 September 2012 04:35
		Re: finding the center of gravity of an irregularly shaped roi within a 2d array By: David Fanning on Mon, 03 September 2012 09:26
		Re: finding the center of gravity of an irregularly shaped roi within a 2d array By: David Fanning on Mon, 03 September 2012 09:24
		Re: finding the center of gravity of an irregularly shaped roi within a 2d array By: ian.j.ashpole on Mon, 03 September 2012 06:58
		Re: finding the center of gravity of an irregularly shaped roi within a 2d array By: David Fanning on Mon, 03 September 2012 06:42

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