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| -rwxr-xr-x | kendalls_tau | 75 |
1 files changed, 75 insertions, 0 deletions
diff --git a/kendalls_tau b/kendalls_tau new file mode 100755 index 0000000..c0c20be --- /dev/null +++ b/kendalls_tau @@ -0,0 +1,75 @@ +#!/usr/bin/env ruby + +################################################# +# reads space delimted pairs of scores as input, +# outputs Kendall's τ +################################################# + +def kendall_with_ties l + concordant = 0 + disconcordant = 0 + tie_a = 0 + tie_b = 0 + l.each_with_index { |k,i| + l[i+1,l.size].each_with_index { |m,j| + if (k.first < m.first && k[1] < m[1]) || + (k.first > m.first && k[1] > m[1]) + concordant += 1 + elsif (k.first == m.first && k[1] != m[1]) + tie_a += 1 + elsif (k.first != m.first && k[1] == m[1]) + tie_b += 1 + else + disconcordant += 1 + end + } + } + + return (concordant-disconcordant)/(Math.sqrt((concordant+disconcordant+tie_a)*(concordant+disconcordant+tie_b))) +end + +def kendall l + concordant = 0 + disconcordant = 0 + l.each_with_index { |k,i| + l[i+1,l.size].each_with_index { |m,j| + if (k.first <= m.first && k[1] <= m[1]) || + (k.first >= m.first && k[1] >= m[1]) + concordant += 1 + else + disconcordant += 1 + end + } + } + + return (concordant-disconcordant)/(0.5 * l.size * (l.size-1)) +end + +def has_ties? l + if l.map{ |p| p[1] }.uniq.size != l.size || + l.map{ |p| p[2] }.uniq.size != l.size + return true + end + + return false +end + +def main + l = [] + while line = STDIN.gets + a,b = line.split + l << [a.to_f, b.to_f] + end + + v = -1 + if has_ties? l + v = kendall_with_ties l + else + v = kendall l + end + + puts v +end + +main + |