[phenixbb] Table 1 stastics

Nathaniel Echols nechols at lbl.gov
Fri Oct 19 08:15:11 PDT 2012

On Fri, Oct 19, 2012 at 8:07 AM, Kay Diederichs
<Kay.Diederichs at uni-konstanz.de> wrote:
> I just want to point out that one possible source of discrepancy between
> I/sigma reported by a data processing program, and I/sigma reported by a
> program that uses the relevant cctbx routine is the following: that cctbx
> routine calculates the variance of merged data as max("internal variance",
> "external variance") which is different from what the data processing
> programs do (they calculate the "internal variance" - I hope I didn't get it
> the wrong way round). SHELXC and SHELXL also calculate the variance of the
> merged data like the data processing programs do.

Good point.  However, this particular CCTBX routine is only used when
merging non-unique data, which would not be the typical input here (at
least in the official release).

> I dislike this "feature" of cctbx but I do not know if phenix.table_one
> actually uses this routine for this purpose.

It does.  But I may change this, if I can be certain it won't screw
things up for the small molecule folks.  I'm just not sure why it was
written that way in the first place...


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