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
[log in to unmask]
212-478-0698
http://www.deshawresearch.com
> -----Original Message-----
> From: CCP4 bulletin board [mailto:[log in to unmask]] On
> Behalf Of Ian Tickle
> Sent: Tuesday, July 29, 2008 5:18 AM
> To: [log in to unmask]
> 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: [log in to unmask]
> > [mailto:[log in to unmask]] On Behalf Of Phil Evans
> > Sent: 29 July 2008 09:11
> > To: [log in to unmask]
> > 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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