On Fri, Jan 25, 2013 at 2:24 AM, Robbie Joosten <robbie_joos...@hotmail.com> wrote: > Phenix however needs to deal with the CCP4 type reflection binning. Now the > size of the sets cannot be used which means that you have find a smarter > solution. So I wonder how this is implemented. Does Phenix use the > (reasonable) assumption that the test set is labeled 1.00 or 0.00? Or does > it also check the sets with other labels?
I forget the exact rules, but the general assumption is that if you have multiple flag values (such as 0 through 19), the test set is marked by the lowest value. If you have just two values, the test set is whichever is less common. (For SHELX files this would typically be -1, for CNS files it would be 1, but you could just as easily swap flag values and it would still pick the correct set.) I'm sure someone can figure out a way to break this (for instance, by assigning the flags with CCP4, but using 7 instead of 0 as the test set), but in practice nearly every file we've seen obeys these rules, and it can of course be overridden by the user. Anyway this is all open-source, so you can check (and re-use!) the logic for yourself here: http://cctbx.svn.sourceforge.net/viewvc/cctbx/trunk/iotbx/reflection_file_utils.py?revision=16491&view=markup -Nat
