The sentence: "then the covariance matrix above gives the statistical error on the best-fit parameters resulting from the Gaussian errors 'sigma_i' on the underlying data 'y_i'."
And here I note the wording: "statistical error" "Gaussian errors" Best Troels 2014-08-29 21:21 GMT+02:00 Troels Emtekær Linnet <tlin...@nmr-relax.com>: > Hi Edward. > > I also think it is some math some where. > > I have a feeling, that it is the creating of Monte Carlo data with 2 sigma? > and then some log/exp calculation of R2eff. > > If the errors are 2 x times over estimated, the chi2 values are 4 as > small, and the > space should be the same? > > best > Troels > > 2014-08-29 17:06 GMT+02:00 Edward d'Auvergne <edw...@nmr-relax.com>: >> I've just added the 2D Grace plots for this to the repository (r25444, >> http://article.gmane.org/gmane.science.nmr.relax.scm/23194). They are >> also attached to the task for easier access >> (https://gna.org/task/index.php?7822#comment107). From these plots I >> see that the I0 error appears to be reasonable, but that the R2eff >> errors are overestimated by 1.9555. >> >> The plots are very, very different. It is clear that >> chi2_jacobian=True just gives rubbish. It is also clear that there is >> a perfect correlation in R2eff when chi2_jacobian=False. The plot >> shows absolutely no scattering, therefore this indicates a crystal >> clear mathematical error somewhere. I wonder where that could be. It >> may not be a factor of 2, as the correlation is 1.9555. So it might >> be a bug that is more complicated. In any case, overestimating the >> errors by ~2 and performing a dispersion analysis is not possible. >> This will significantly change the curvature of the optimisation space >> and will also have a huge effect on statistical comparisons between >> models. >> >> Regards, >> >> Edward >> >> >> >> On 29 August 2014 16:56, Troels Emtekær Linnet <tlin...@nmr-relax.com> wrote: >>> The default is now chi2_jacobian=False. >>> >>> You will hopefully see, that the errors are double. >>> >>> Best >>> Troels >>> >>> 2014-08-29 16:43 GMT+02:00 Edward d'Auvergne <edw...@nmr-relax.com>: >>>> Terrible ;) For R2eff, the correlation is 2.748 and the points are >>>> spread out all over the place. For I0, the correlation is 3.5 and the >>>> points are also spread out everywhere. Maybe I should try with the >>>> change from: >>>> >>>> relax_disp.r2eff_err_estimate(chi2_jacobian=True) >>>> >>>> to: >>>> >>>> relax_disp.r2eff_err_estimate(chi2_jacobian=False) >>>> >>>> How should this be used? >>>> >>>> Cheers, >>>> >>>> Edward >>>> >>>> >>>> >>>> On 29 August 2014 16:33, Troels Emtekær Linnet <tlin...@nmr-relax.com> >>>> wrote: >>>>> Do you mean terrible or double? >>>>> >>>>> Best >>>>> Troels >>>>> >>>>> 2014-08-29 16:15 GMT+02:00 Edward d'Auvergne <edw...@nmr-relax.com>: >>>>>> Hi Troels, >>>>>> >>>>>> I really cannot follow and judge how the techniques compare. I must >>>>>> be getting old. So to remedy this, I have created the >>>>>> test_suite/shared_data/dispersion/Kjaergaard_et_al_2013/exp_error_analysis/ >>>>>> directory (r25437, >>>>>> http://article.gmane.org/gmane.science.nmr.relax.scm/23187). This >>>>>> contains 3 scripts for comparing R2eff and I0 parameters for the 2 >>>>>> parameter exponential curve-fitting: >>>>>> >>>>>> 1) A simple script to perform Monte Carlo simulation error analysis. >>>>>> This is run with 10,000 simulations to act as the gold standard. >>>>>> >>>>>> 2) A simple script to perform covariance matrix error analysis. >>>>>> >>>>>> 3) A simple script to generate 2D Grace plots to visualise the >>>>>> differences. Now I can see how good the covariance matrix technique >>>>>> is :) >>>>>> >>>>>> Could you please check and see if I have used the >>>>>> relax_disp.r2eff_err_estimate user function correctly? The Grace >>>>>> plots show that the error estimates are currently terrible. >>>>>> >>>>>> Cheers, >>>>>> >>>>>> Edward >>>>>> >>>>>> _______________________________________________ >>>>>> relax (http://www.nmr-relax.com) >>>>>> >>>>>> This is the relax-devel mailing list >>>>>> relax-devel@gna.org >>>>>> >>>>>> To unsubscribe from this list, get a password >>>>>> reminder, or change your subscription options, >>>>>> visit the list information page at >>>>>> https://mail.gna.org/listinfo/relax-devel _______________________________________________ relax (http://www.nmr-relax.com) This is the relax-devel mailing list relax-devel@gna.org To unsubscribe from this list, get a password reminder, or change your subscription options, visit the list information page at https://mail.gna.org/listinfo/relax-devel
