And the little jiffy program you want Phil is calc-ax (Version 951120)
by Joachim Meyer, University of Freiburg, Germany, which takes an RT mtx
(in OMAT format), and gives back all kinds of useful info.

A google search didn't turn this program up on the web, or Dr. Meyer;
original & my slightly modified code attached, & binary for linux.

Dave

David Borhani, Ph.D.
D. E. Shaw Research, LLC
120 West Forty-Fifth Street, 39th Floor
New York, NY 10036
[EMAIL PROTECTED]
212-478-0698
http://www.deshawresearch.com



> -----Original Message-----
> From: CCP4 bulletin board [mailto:[EMAIL PROTECTED] On 
> Behalf Of Ian Tickle
> Sent: Tuesday, July 29, 2008 5:18 AM
> To: [email protected]
> Subject: Re: [ccp4bb] Rotation axis
> 
> Hi Phil
> 
> The rotation axis is the locus of points which the 
> transformation leaves
> unmoved, i.e. the eigenvector of the transformation matrix which has a
> unit eigenvalue.  So writing the transformation in 
> homogeneous form for
> convenience: x' = Sx you need to solve x' = x, or Sx = x, either
> analytically or just plug the matrix S into a canned eigenvector
> routine.
> 
> Cheers
> 
> -- Ian
> 
> > -----Original Message-----
> > From: [EMAIL PROTECTED] 
> > [mailto:[EMAIL PROTECTED] On Behalf Of Phil Evans
> > Sent: 29 July 2008 09:11
> > To: [email protected]
> > Subject: Rotation axis
> > 
> > If I've go a superposition transformation (x' = Rx + t), as 
> > it happens  
> > from a superposition in ccp4mg, how do I get the position & 
> > direction  
> > of the rotation axis (to draw in a picture)?
> > I know that any (orthonormal) transformation can be 
> represented as a  
> > rotation about an axis + a screw translation along that axis
> > 
> > I'm sure I've done this before ...
> > 
> > thanks
> > Phil
> > 
> > 
> 
> 
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Description: calc-ax.tgz

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