Hi Oleg, Thanks. My Python function for the first derivative is (happily) identical in form. Such a function does seem like something of general utility that should perhaps be present in scitbx. Or maybe situations that require this are actually quite rare. The code from David Thomas (e.g. RTMATS in Mosflm source) is nice because it does explicit calculation of up to the fourth derivative, after which they repeat. Although the need for that must surely be rather unusual. Cheers -- David On 28 June 2012 11:34, Oleg Dolomanov wrote:

Hi David,

I did these some times ago, you can find them here:

For rotation around a vector:

http://cctbx.svn.sourceforge.net/viewvc/cctbx/trunk/smtbx/refinement/constraints/shared.cpp?revision=13167&view=markup

at line 76 For 3 Euler angles:

http://cctbx.svn.sourceforge.net/viewvc/cctbx/trunk/smtbx/refinement/constraints/same_group.cpp?revision=13935&view=markup

at line 107

Also these derivatives present here:

http://cctbx.svn.sourceforge.net/viewvc/cctbx/trunk/smtbx/refinement/constraints/rigid.cpp?revision=12381&view=markup

at lines 61 and 130

Cheers,

Oleg. ------------------------------ From: [email protected] Date: Thu, 28 Jun 2012 11:13:45 +0100 To: [email protected] Subject: [cctbxbb] angle derivative of rotation matrix

Hi,

I'm using the axis_and_angle_as_r3_rotation_matrix method of scitbx.matrix.col in some Python code. Now I need to calculate the first derivative of the rotation matrix with respect to the rotation angle. Is there a function to do that somewhere in scitbx (or elsewhere in cctbx)? I had a brief look around but couldn't find anything that looked hopeful.

If there isn't something there already I have some Fortran code from David Thomas that I could adapt to do this. Of course it wouldn't be very efficient in pure Python, and calculating the matrix and its derivative separately, but that's okay for now as the code is just for testing out some ideas.

By the way, links to http://skal.planet-d.net/demo/matrixfaq.htm in the documentation (e.g. herehttp://cctbx.sourceforge.net/current/c_plus_plus/namespacescitbx_1_1math_1_1...) are broken. I found a document with the same name here: http://vamos.sourceforge.net/matrixfaq.htm, but I have no idea if this has the same content as the original.

Cheers

-- David

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Ok, once I get to needing an efficient version (still some way off that) I'll write it in C++ with nth order derivative calculation and put it in scitbx. Cheers -- David On 28 June 2012 14:45, Pavel Afonine wrote:

Such a function does seem like something of general utility that should

...

perhaps be present in scitbx.

Sounds like a good idea. Pavel

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