Hi Martin, All,
   There are some other formulas that you can find here and there but to
the best of my knowledge they're all equivalent. In all cases R-squared
should be non-negative (read the attached file).

Best regards,
Pantelis


On Wed, 2011-07-13 at 10:50 +0200, Martin Guetlein wrote:
> Hey Pantelis,
> 
> we are having a internal discussion which r-square computation is the
> right one. Do you have a opinion on that?
> 
> Regards,
> Martin
> 
> 
> On Tue, May 24, 2011 at 10:12 AM, Martin Guetlein
> <martin.guetlein at googlemail.com> wrote:
>         Hello All,
>         
>         I just changed the r-square computation within the validation
>         service. So far I used the squared sample correlation
>         coefficient. However, it seems that the more common way to
>         compute r-square is 1 - SSE/SST (thats how it is computed in R
>         as well).
>         I updated the validation statistics page
>         (http://opentox.org/data/documents/development/validation/validation-statistics) accordingly.
>         
>         Best regards,
>         Martin
>         
>         
>         P.S. some links
>         r-square definitions:
>         http://web.maths.unsw.edu.au/~adelle/Garvan/Assays/GoodnessOfFit.html
>         http://en.wikipedia.org/wiki/Coefficient_of_determination#Definitions
>         r-square as squared sample correlation coefficient
>         http://mathworld.wolfram.com/CorrelationCoefficient.html
>         
>         
>         -- 
>         Dipl-Inf. Martin Gütlein
>         Phone:
>         +49 (0)761 203 8442 (office)
>         +49 (0)177 623 9499 (mobile)
>         Email:
>         guetlein at informatik.uni-freiburg.de
> 
> 
> 
> -- 
> Dipl-Inf. Martin Gütlein
> Phone:
> +49 (0)761 203 7633 (office)
> +49 (0)177 623 9499 (mobile)
> Email:
> guetlein at informatik.uni-freiburg.de

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