[phenixbb] refinement with anomalous data

[Pavel Afonine]

Once again, you cannot compare R factors calculated using different sets 
of data.
Pavel

On 2/6/15 11:48 AM, Guangyu Zhu wrote:
> That’s how I think. But say if I+ is exactly same as I-, I use it 
> twice. I got much lower R and Rfree, that means better fit. Isn’t 
> good? And I’m also curious why.
>
> Guangyu
>
> From: Pavel Afonine <pafonine at lbl.gov <mailto:pafonine at lbl.gov>>
> Date: Friday, February 6, 2015 at 2:29 PM
> To: Guangyu Zhu <gzhu at hwi.buffalo.edu <mailto:gzhu at hwi.buffalo.edu>>, 
> "phenixbb at phenix-online.org <mailto:phenixbb at phenix-online.org>" 
> <phenixbb at phenix-online.org <mailto:phenixbb at phenix-online.org>>
> Subject: Re: [phenixbb] refinement with anomalous data
>
> If data set isn't anomalous then I don't see why you would want to 
> refine against I+/I-.
> Pavel
>
> On 2/6/15 11:26 AM, Guangyu Zhu wrote:
>> What I meant is: I actually don’t have anomalous signal, so when I 
>> use I+/I-, kind of like I use Imean twice for each reflection. Can I 
>> do that?  My guess is that the resolution is low, so double 
>> reflection/parameter ratio really benefits the refinement, although 
>> overall the weight for x-ray term is not change, because rms bond and 
>> angle are similar.
>>
>> Newer versions are better for my other refinement with higher 
>> resolution, but not this data set.
>>
>> Guangyu
>>
>> From: Pavel Afonine <pafonine at lbl.gov <mailto:pafonine at lbl.gov>>
>> Date: Friday, February 6, 2015 at 2:12 PM
>> To: Guangyu Zhu <gzhu at hwi.buffalo.edu <mailto:gzhu at hwi.buffalo.edu>>, 
>> "phenixbb at phenix-online.org <mailto:phenixbb at phenix-online.org>" 
>> <phenixbb at phenix-online.org <mailto:phenixbb at phenix-online.org>>
>> Subject: Re: [phenixbb] refinement with anomalous data
>>
>>
>>> I use same data set for refinement, so Rfree is also marked for same 
>>> reflection. The only difference is that I chose “Data labels” from 
>>> Phenix IMEAN or I(+) I(-).
>>
>> What I meant is that the IMEAN set is not the same as I(+),I(-) at 
>> least because the number of reflections in IMEAN is not the same as 
>> in I(+),I(-).
>>
>>> By the way, I use version 1.8.2 for refinement. Newer versions gives 
>>> higher R/Rfree.
>>
>> Should be the other way around...
>>
>> Pavel
>>
>

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