HI Jacob
Yes, I got this - and I appreciate the benefit of Rmeas for dealing with
measuring agreement for small-multiplicity observations. Having this *as well*
is very useful and I agree Rmeas / Rpim / CC-half should be the primary
“quality” statistics.
However, you asked if there is any reason to *keep* rather than *eliminate*
Rmerge, and I offered one :o)
I do not see what harm there is reporting Rmerge, even if it is just used in
the inner shell or just used to capture a flavour of the data set overall. I
also appreciate that Rmeas converges to the same value for large multiplicity
i.e.:
Overall InnerShell OuterShell
Low resolution limit 39.02 39.02 1.39
High resolution limit 1.35 6.04 1.35
Rmerge (within I+/I-) 0.080 0.057 2.871
Rmerge (all I+ and I-) 0.081 0.059 2.922
Rmeas (within I+/I-) 0.081 0.058 2.940
Rmeas (all I+ & I-) 0.082 0.059 2.958
Rpim (within I+/I-) 0.013 0.009 0.628
Rpim (all I+ & I-) 0.009 0.007 0.453
Rmerge in top intensity bin 0.050 - -
Total number of observations 1265512 16212 53490
Total number unique 17515 224 1280
Mean((I)/sd(I)) 29.7 104.3 1.5
Mn(I) half-set correlation CC(1/2) 1.000 1.000 0.778
Completeness 100.0 99.7 100.0
Multiplicity 72.3 72.4 41.8
Anomalous completeness 100.0 100.0 100.0
Anomalous multiplicity 37.2 42.7 21.0
DelAnom correlation between half-sets 0.497 0.766 -0.026
Mid-Slope of Anom Normal Probability 1.039 - -
(this is a good case for Rpim & CC-half as resolution limit criteria)
If the statistics you want to use are there & some others also, what is the
pressure to remove them? Surely we want to educate on how best to interpret the
entire table above to get a fuller picture of the overall quality of the data?
My 0th-order request would be to publish the three shells as above ;o)
Cheers Graeme
> On 4 Jul 2017, at 22:09, Keller, Jacob <[email protected]> wrote:
>
> I suggested replacing Rmerge/sym/cryst with Rmeas, not Rpim. Rmeas is simply
> (Rmerge * sqrt(n/n-1)) where n is the number of measurements of that
> reflection. It's merely a way of correcting for the multiplicity-related
> artifact of Rmerge, which is becoming even more of a problem with data sets
> of increasing variability in multiplicity. Consider the case of comparing a
> data set with a multiplicity of 2 versus one of 100: equivalent data quality
> would yield Rmerges diverging by a factor of ~1.4. But this has all been
> covered before in several papers. It can be and is reported in resolution
> bins, so can used exactly as you say. So, why not "disappear" Rmerge from the
> software?
>
> The only reason I could come up with for keeping it is historical reasons or
> comparisons to previous datasets, but anyway those comparisons would be
> confounded by variabities in multiplicity and a hundred other things, so come
> on, developers, just comment it out!
>
> JPK
>
>
>
>
> -----Original Message-----
> From: [email protected] [mailto:[email protected]]
> Sent: Tuesday, July 04, 2017 4:37 PM
> To: Keller, Jacob <[email protected]>
> Cc: [email protected]
> Subject: Re: [ccp4bb] Rmergicide Through Programming
>
> HI Jacob
>
> Unbiased estimate of the true unmerged I/sig(I) of your data (I find this
> particularly useful at low resolution) i.e. if your inner shell Rmerge is 10%
> your data agree very poorly; if 2% says your data agree very well provided
> you have sensible multiplicity… obviously depends on sensible interpretation.
> Rpim hides this (though tells you more about the quality of average
> measurement)
>
> Essentially, for I/sig(I) you can (by and large) adjust your sig(I) values
> however you like if you were so inclined. You can only adjust Rmerge by
> excluding measurements.
>
> I would therefore defend that - amongst the other stats you enumerate below -
> it still has a place
>
> Cheers Graeme
>
>> On 4 Jul 2017, at 14:10, Keller, Jacob <[email protected]> wrote:
>>
>>> Rmerge does contain information which complements the others.
>>
>> What information? I was trying to think of a counterargument to what I
>> proposed, but could not think of a reason in the world to keep reporting it.
>>
>> JPK
>>
>>
>> On 4 Jul 2017, at 12:00, Keller, Jacob
>> <[email protected]<mailto:[email protected]>> wrote:
>>
>> Dear Crystallographers,
>>
>> Having been repeatedly chagrinned about the continued use and reporting of
>> Rmerge rather than Rmeas or similar, I thought of a potential way to promote
>> the change: what if merging programs would completely omit Rmerge/cryst/sym?
>> Is there some reason to continue to report these stats, or are they just
>> grandfathered into the software? I doubt that any journal or
>> crystallographer would insist on reporting Rmerge per se. So, I wonder what
>> developers would think about commenting out a few lines of their code,
>> seeing what happens? Maybe a comment to the effect of "Rmerge is now
>> deprecated; use Rmeas" would be useful as well. Would something catastrophic
>> happen?
>>
>> All the best,
>>
>> Jacob Keller
>>
>> *******************************************
>> Jacob Pearson Keller, PhD
>> Research Scientist
>> HHMI Janelia Research Campus / Looger lab
>> Phone: (571)209-4000 x3159
>> Email: [email protected]<mailto:[email protected]>
>> *******************************************
>>
>>
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