Hi Graeme, There's a very nice page on the (unofficial?) CCP4 wiki about it http://strucbio.biologie.uni-konstanz.de/ccp4wiki/index.php/Test_set
For structures with a lot of reflections, a rule of thumb would be that 2000 free reflections would give an adequate reliability in the free R factor. Hope this helps, Folmer Fredslund 2015-06-02 12:26 GMT+02:00 Graeme Winter <[email protected]>: > Hi Folks > > Had a vague comment handed my way that "xia2 assigns too many free > reflections" - I have a feeling that by default it makes a free set of 5% > which was OK back in the day (like I/sig(I) = 2 was OK) but maybe seems > excessive now. > > This was particularly in the case of high resolution data where you have a > lot of reflections, so 5% could be several thousand which would be more > than you need to just check Rfree seems OK. > > Since I really don't know what is the right # reflections to assign to a > free set thought I would ask here - what do you think? Essentially I need > to assign a minimum %age or minimum # - the lower of the two presumably? > > Any comments welcome! > > Thanks & best wishes Graeme > -- Folmer Fredslund
