[R] setting weights for such a two-class problem in nnet and svm
Prof Brian Ripley
ripley at stats.ox.ac.uk
Fri Jul 22 18:56:12 CEST 2005
On Fri, 22 Jul 2005, Baoqiang Cao wrote:
> Dear All,
> I have such a two-class problem, one class is very large(~98% of total),
> and the other is just 2%. According to manual of nnet, I need setup
> "weights", so I intend to set 1 for class one, 49 for class 2. How do I
> do that? Just weights=49?
I do not know what you mean by `manual of nnet', but no, not that since
the help page says
weights: (case) weights for each example - if missing defaults to 1.
More likely you want ifelse(class==1, 1/49, 1).
However, there is more to it than that, and do please read the reference
books on the help page.
Brian D. Ripley, ripley at stats.ox.ac.uk
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595
More information about the R-help