Re: [ccp4bb]: Truncate Resolution Error

["M.D.Winn" <M.D.Winn@dl.ac.uk>]

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> "Eleanor J. Dodson" wrote:
> > >
> > > TRUNCATE:  *** Data beyond useful resolution limit ***
> > >
> > 
> >  Well - it means you have a bin where the <I> is <= 0.0. Which indeed is
> > tantamount to having indexed your data beyons a useful resolution
> > limit..
> > 
> I would like to see this become a warning which could be
> ignored at the user's discretion (unless this would completely
> invalidate the French & Wilson treatment). When working at

I don't think this would work. The truncate procedure uses
an interpolated value of the mean intensity in a Wilson distribution,
which is used as prior knowledge. A negative value of this mean
intensity would presumably screw up the Wilson distribution, and
hence the whole procedure. In fact, the code forces it to be
at least a little positive:

      SIGMA = MAX(SIGMA,0.1)

so it might give you wrong answers instead of crashing...

Martyn


> Very Low Resolution, the data do not fall off monotonically
> with resolution, but have a distinct trough around 6A and peak 
> near 5A. When we have struggled to improve the resolution to 
> the point that we can see clearly useable data around 5A, it is 
> discouraging to be told by truncate that we can't use it 
> because there is a bin with <I> negative around 6 A. 
> Usually we can get around this by playing with the 
> bin size until no bin has negative <I>, but this is 
> tedious and artificial.
> 
> Ed
> 


-- 


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*                  Dr. Martyn Winn                                       *
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