Dear Eleanor, Thanks for pointing out that CCP4 FreeRflag selects the test set in the highest possible symmetry for the crystal class! I didn't know that.
The following sentences (which are somewhat difficult to understand for me) in https://www.ccp4.ac.uk/html/freerflag.html appear to document that: "The FreeR_flag is randomly and uniformly distributed reflexion-by-reflexion, but, additionally, if the keyword NOSYM is not set, all reflections that are equivalent by the symmetry of the point group of the twin lattice (assuming the data is twinned), obtain the same flag. This includes both the possibility of merohedral and pseudomerohedral twinning. In the latter case, the obliquity parameter can be set using the keyword OBL." I wonder since which CCP4 version (or date) this is the default behaviour. best wishes, Kay On Mon, 30 Aug 2021 18:28:23 +0100, Eleanor Dodson <eleanor.dod...@york.ac.uk> wrote: >Back to FreeR factors - Phenix, and I believe FreeRflag now select FreeRs >in the highest possible symmetry for the crystal class - eh P6/mmm for a >trigonal crystal, and expand the set to fill the actual space group. This >means the Free R assignment is suitable if later the crystal symmetry is >reassigned. But this was not always done in the past so if you are trying >to reuse free/work assignments from an old project there are possibilities >of not getting this. Maybe the best solution is to just generate a new Free >R set ? >Eleanor > ... ######################################################################## To unsubscribe from the CCP4BB list, click the following link: https://www.jiscmail.ac.uk/cgi-bin/WA-JISC.exe?SUBED1=CCP4BB&A=1 This message was issued to members of www.jiscmail.ac.uk/CCP4BB, a mailing list hosted by www.jiscmail.ac.uk, terms & conditions are available at https://www.jiscmail.ac.uk/policyandsecurity/
