[ccp4bb]: Ranom in Scala

[Dr Nicholas Keep <n.keep@mail.cryst.bbk.ac.uk>]

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I am processing nearly 180 degrees of data from a crystal which I
believe to be P422 (hence I have very high redundancy).  I am perplexed
by the behaviour of Ranom in Scala.  Processing my data gives Rfac in
the outer bin of .375 Rfull of 0.358 and Ranom of 0.10.  This made me
wonder if the crystal was not showing the full symmetry at the high
resolution as the anomalous data is so much 'better' so I reprocessed in
P1 (still fairly complete data).  This only dropped the Rfac in the
outer bin to 0.227 rfull to 0.246 but increased Ranom to 0.303.  These
trends generally hold in the lower resolution bins and for the peak and
remote wavelengths.

Is the explaination of this that the Ranom is based on the average I+
and I- for the merged equivalents rather than the matched Bijvoet pairs
for a particular index before merging?

Thanks 
Nick



-- 
Dr Nicholas H. Keep
Department of Crystallography,
Birkbeck College,
University of London,
Malet Street,
LONDON
WC1E 7HX

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