Hi Jan, There are two steps to think about: .map_to_asu() and .common_set() or .common_sets(). Look for these methods in cctbx/regression/tst_miller.py, then add print statements to see how they work (run the command with e.g. "P31" so that it only exercisesone space group). However, the best way to compute f_calc given an array of f_obs is via   f_calc = f_obs.structure_factors_from_scatterers(     xray_structure).f_calc() This way the f_calc are directly compatible with the f_obs array. Ralf

________________________________ From: Jan Marten Simons To: [email protected] Sent: Monday, April 11, 2011 3:00 AM Subject: Re: [cctbxbb] Best way to compare incomplete f_hkl to calculated f_hkl

Hi,

I'm looking at the best (=fastest) way to compare a (possibly incomplete) list of observed reflections f_hkl_obs (or fo2_hkl_obs) to the f_hkl_calc of  calculated structure factors or intensities from a model structure.

in miller.py there is a function to calculate a difference between f_obs and f_calc, but it asserts that all reflections are present in f_obs:

def f_obs_minus_f_calc(self, f_obs_factor, f_calc): assert f_calc.is_complex_array() assert self.indices().all_eq(f_calc.indices()) assert self.anomalous_flag() is f_calc.anomalous_flag() ...

In my case it's possible that some reflections could not be observed so they should either be skipped or be assumed to be of zero intensity. As I could not locate the definition for .all_eq(...), yet I'm not sure if this is already handled and if it is how it is done.

Then there is f_obs_minus_xray_structure_f_calc in miller.py as well. Would this be a better approach if the model structure changes quite often? What if I just got f_calc from another source (like doing some custom sped-up partial structure factor calculation)?

In general: What would be your advice on this with cctbx?

With regards,

Dipl. Phys.   Jan M. Simons

Institute of Crystallography RWTH Aachen University _______________________________________________ cctbxbb mailing list [email protected] http://phenix-online.org/mailman/listinfo/cctbxbb