[Chimera-users] Calculating the center of mass of a ligand

[Eric Pettersen]

Hi JD,
	There is no built-in center of mass method in Chimera.  If you've  
selected the atoms beforehand, then the below Python code will  
calculate the center of mass:

from chimera import selection, Vector
sum = 0
center = Vector(0, 0, 0)
for a in selection.currentAtoms():
	sum += a.element.mass
	center += a.element.mass * Vector(*a.coord().data())
print "center of mass:", center / sum

I've also attached it as a file that you can just use File...Open (or  
"open") to run.

--Eric

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On Nov 13, 2007, at 7:18 AM, Jean-Didier Mar?chal wrote:

> Hi everyone,
>
> I have another question: what would be the easiest way to calculate  
> the
> center of mass of a given set of atoms? In particular, is there a  
> python
> module that already has this function implemented?
> I am interested in particular to find the center of mass of a ligand
> bound to a protein.
>
> Thanks a lot,
> JD
>
>
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