> The Spider Objects

>            WILCOXON object

>         A=wilcoxon(D,[L]) calculates the statistical significance of the median
>         loss being greater than competitors for groups of results (data objects)
>         D, with loss function/type L.

>         NOTE: Assumes you have the Matlab stats package, uses signrank.

>         Examples:
>           d=gen(toy);
>           wilcoxon(train(cv({svm knn}),d))     or is equivalent to below
>           train(wilcoxon(cv({svm knn})),d)     or is equivalent to below
>           train(chain({ group(cv({svm knn}),'all') wilcoxon  }),d)