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The CCanom is interesting, but surely such a change in twin fraction will be visible in other statistics as well? Shouldn't the Rmerge/ R pim/ etc show the effect more dramatically?? 

And it still isn't clear to me why this twinning results in a consistent negative CCanom?  I had always suspected negative CCanom reflected inadequate scaling, but it must be related to the space group, and to the multiplicity? 

eleanor

On 16 July 2015 at 20:12, Keller, Jacob <[log in to unmask]> wrote:
Just a footnote--here are the refined twin fractions (Refmac):

000-090 Twin fractions                =    0.3478   0.6522
090-180 Twin fractions                =    0.5207   0.4793

Sorry to spam, but I thought it might be interesting to the 'BB

JPK

Ps The question is "now what?" I assume there is no software for fitting a smoothly-varying twin fraction estimate as a function of phi?








-----Original Message-----
From: Keller, Jacob
Sent: Thursday, July 16, 2015 2:17 PM
To: [log in to unmask]
Subject: RE: Negative CCanom

I think this might explain it: twin fractions are varying through the course of the runs due to variability of crystal illumination. So I compared first 90 deg to second, got the results below. I wonder whether this happens often in twinning cases in which the crystal is not fully immersed (my case, unfortunately (home source, big crystal)).

JPK


======================================================

#### 0-90 degrees:

Twin fraction estimates excluding operators
  Twin fraction estimate from L-test:  0.23
  Twin fraction estimate from moments: 0.25

Twin fraction estimates by operator

---------------------------------------------------------------------------------------
|                                 operator | L-test | H-test | Murray | ML Britton    |
---------------------------------------------------------------------------------------
|                              -h-k, k, -l |   Yes  |  0.32  |  0.3  |  0.3 ( N/A ) |
---------------------------------------------------------------------------------------
TWINNING SUMMARY

Twinning fraction from H-test:   0.32
L-statistic from L-Test:         0.40


======================================================

#### 90-180 degrees:

Twin fraction estimates excluding operators
  Twin fraction estimate from L-test:  0.25
  Twin fraction estimate from moments: 0.29

Twin fraction estimates by operator

---------------------------------------------------------------------------------------
|                                 operator | L-test | H-test | Murray | ML Britton    |
---------------------------------------------------------------------------------------
|                              -h-k, k, -l |   Yes  |  0.42  |  0.39  |  0.45 ( N/A ) |
---------------------------------------------------------------------------------------
TWINNING SUMMARY

Twinning fraction from H-test:   0.42
L-statistic from L-Test:         0.40