Re: [ccp4bb] Cross-validation when test set is miniscule

2014-12-20 Thread Axel Brunger
Dear Derek, I suggest you try 10% for the test set. You should still be able to judge the effect of various restraints (or constraints) as long as you keep the same test set. If you switch test sets, and re-refine, Rfree might change as much as 2% for a test set consisting of 200 reflections

[ccp4bb] Cross-validation when test set is miniscule

2014-12-19 Thread Derek Logan
Hi everyone, Right now we have one of those very difficult Rfree situations where it's impossible to generate a single meaningful Rfree set. Since we're in a bit of a hurry with this structure it would be good if someone could point me in the right direction. We have crystals with 1542 non-H

[ccp4bb] Cross-validation when test set is miniscule

2014-12-19 Thread dusan turk
Dear Derek, I suggest you not not use the cross validation at all. With small data sets the refinement with cross validation is very unstable and the choice of the TEST set dependent. We explained why and suggested to use an alternative function, which can use all data in refinement. Acta