For some small sample sizes I would like to exemplify the combinatorics
underlying certain nonparametric tests like Mann-Whitney-Wilcoxon,
Kruskal-Wallis and Spearman's rank correlation. I have written a
function all.perm which delivers all permutations of 1,2,...,n and
which works reasonably well. This can be used to generate P(R=r) of
Spearman's rank correlation:
n_6;plot(table(apply(all.perm(n),1,cor,y=1:n)),type="h")
all.perm_function(n){
p_matrix(1,ncol=1)
for(i in 2:n){p_pp_cbind(p,i)
v_c(1:i,1:(i-1))
for(j in 2:i){v_v[-1]
p_rbind(p,pp[,v[1:i]])}}
p}
Until now I hesitated to dwell on writing functions to generate all
n!/(k!(n-k)!) k-combinations of an n-element set or more generally all
n!/(k_1!k_2!...n_k!) choices of placing n objects into k boxes where
box j has n_j objects.
Not intending to re-invent the wheel I turn to the R community to ask
if someone has already written these functions.
Any help is thankfully appreciated.
--- D.Trenkler ---
************************************************************************
*********
Dietrich Trenkler
(trenkler at oec.uni-osnabrueck.de)
Statistik / Empirische Wirtschaftsforschung
Universitaet Osnabrueck
Rolandstrasse 8 Phone: +49(0)
541-969-2753
D-49069 Osnabrueck Fax : +49(0) 541-969-2744
GERMANY
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