On 3 June 2016 at 12:08, Edward d'Auvergne <edw...@nmr-relax.com> wrote:
> Hi Petr,
> For the new bug report at https://gna.org/bugs/?24675, now looking at
> the results I can see that this is actually quite a deliberate
> feature.  For reference, I will attach the plots for residues 133 and
> 134 for the CR2 model as a PDF file to that bug report
> (disp_CKIRD_133_N.pdf and disp_CKIRD_134_N.pdf).  For residue 133,
> there the blue line can be seen to be the dispersion curve predicted
> for the missing 600 MHz data.  For 134, the green line is the
> predicted dispersion curve for the 950 MHz data.
> The R20 values come from the fitting of the single field strength data
> points, and this value is independent of field strength.  So the
> predicted curves are perfectly correct - they are exactly where they
> are supposed to be.  Assuming the model to be correct, the predicted
> curves are what the real data should look like.  So the curves without
> measured data are actually quite powerful tools for investigating why
> the data is missing.  They are also useful for investigating how well
> the model fits to single field strength data.  It is also quite easy
> in Grace to double click on the curve and hide it, if desired.
> Therefore I think I'll leave the plotting code as it is.

Hi Petr,

Sorry, the R20 values are field strength dependent, but both are fit
during the optimisation of the dispersion models with missing data.
This is problematic as one parameter is undefined - the R20 for the
missing field - and this interferes with optimisation algorithms.  The
undefined R20 value can float around to any value, and this breaks the
rules that most algorithms absolutely rely on.  Hence the solution
found is unlikely to be the minimum in the optimisation space.  I
would therefore suggest deselecting these spins for now, as the
results are nonsensical.  It might take me a while to update each part
of relax to detect the missing data for one entire field strength from
the N fields, and drop back to N-1 fields.  This bug might take a
while to fix!  I might have to spend a few days working on that one
next week.



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