Derivation but no reference except truncate is in BMC page 330 sidebar. Probably read the source code or some prog. ref….
BR From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of Jonathan Cooper Sent: Tuesday, May 26, 2015 4:33 PM To: CCP4BB@JISCMAIL.AC.UK Subject: [ccp4bb] reference needed for "TRUNCATE NO" equation. Dear all I have been asked by Randy for a reference for the following equation which appears in Sherwood & Cooper: http://www.ucl.ac.uk/~rmhajc0/truncate_no.jpg ... or in text form: sigma(F) = sqrt(I + sigma(I)) - sqrt(I) It is the equation which TRUNCATE uses to calculate sigma(|F|) if the user switches off the French-Wilson treatment, although that is never usually done! Can anyone shed any light on who derived it and where/whether it has been published, etc? Cheers for now. Jon Cooper
