ligges at statistik.uni-dortmund.de
Wed Mar 29 14:31:17 CEST 2006
Sven Schaltenbrand wrote:
> dear list,
> i have a problem using the adaboost function from the package boost.
> running the example of leukemia works out very well, but so it does not on
> my own data.
> i always get the following 22 warnings:
> 1: cannot compute exact p-value with ties in: wilcox.test.default(x[which(y
> == 0)], x[which(y == 1)])
> can anybody please help me with the meaning of this warning.
As far as I understand, adaboost() uses the Wilcoxon test statistic as
some measure to do variable preselection.
Since you can adjust how many "features" should be selected, it seems to
be less important to obtain *exact* p-values and you can ignore the
warning. Nevertheless it makes sense to look into your data where the
ties come from ...
> thnak you
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