> I don't know the justification; maybe just experience? Surely the higher the > better. I've seen George Sheldrick deriving the value of ~0.8 when there is > _no_ anom signal but I forgot the details, sorry ...
It is derived from the mean absolute error (cf. p414 in Chapter 8 of BMC, with help of Ian Tickle), and holds for unmerged data. A reasonable good indication where to set the cutoff in practice is to look at the site vs occupancy plot. A distinct drop after a few good sites is usually a good sign, and that tends to cluster around the ~1.3 ratio. http://www.ruppweb.org/Garland/gallery/Ch10/pages/Biomolecular_Crystallography_Fig_10-30_PART2.htm The noise level is actually observable in data without anomalous signal http://www.ruppweb.org/Garland/gallery/Ch10/pages/Biomolecular_Crystallography_Fig_10-29.htm Best BR best wishes, Kay > >Thanks! >-- David > >####################################################################### ># > >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/ > ######################################################################## 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/ ######################################################################## 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/
