[R] compositional data: percent values sum up to 1

[Christoph Lehmann]

I want to do a logistic regression analysis, and to compare with, a
discriminant analysis. The mentioned power maps are my exogenous data,
the dependent variable (not mentioned so far) is a diagnosis
(ill/healthy)

thanks for the interest and the help

Christoph

On Sun, 2003-06-01 at 21:01, Spencer Graves wrote:
> What are you trying to do?  What I would do with this depends on many 
> factors.
> 
> spencer graves
> 
> Christoph Lehmann wrote:
> > again, under another subject:
> > sorry, maybe an all too trivial question. But we have power data from J
> > frequency spectra and to have the same range for the data of all our
> > subjects, we just transformed them into % values, pseudo-code:
> > 
> > power[i,j]=power[i,j]/sum(power[i,1:J])
> > 
> > of course, now we have a perfect linear relationship in our x design-matrix,
> > since all power-values for each subject sum up to 1.
> > 
> > How shall we solve this problem: just eliminate one column of x, or
> > introduce a restriction which says exactly that our power data sum up to
> > 1 for each subject?
> > 
> > Thanks a lot
> > 
> > Christoph
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://www.stat.math.ethz.ch/mailman/listinfo/r-help
-- 
Christoph Lehmann <christoph.lehmann at gmx.ch>