math.statistics: adding contraharmonic-mean.

diff --git a/basis/math/statistics/statistics-tests.factor b/basis/math/statistics/statistics-tests.factor
index de5ffa84acb75b57356b2a6ba2d01c401cee36a4..8e28a463f7ec83cee021bf2c48ea850ae70906c5 100644 (file)
--- a/basis/math/statistics/statistics-tests.factor
+++ b/basis/math/statistics/statistics-tests.factor
@@ -8,6 +8,7 @@ IN: math.statistics.tests
 [ t ] [ { 2 2 2 2 } geometric-mean 2.0 .0001 ~ ] unit-test
 [ 1.0 ] [ { 1 1 1 } geometric-mean ] unit-test
 [ 1/3 ] [ { 1 1 1 } harmonic-mean ] unit-test
+[ 5+1/4 ] [ { 1 3 5 7 } contraharmonic-mean ] unit-test
 
 [ 0 ] [ { 1 } range ] unit-test
 [ 89 ] [ { 1 2 30 90 } range ] unit-test

diff --git a/basis/math/statistics/statistics.factor b/basis/math/statistics/statistics.factor
index dad1f75ce681f941954ed1ec9369d4147af7453f..1ab5760fa6c6307cf2076e1a1649b4529d819e18 100644 (file)
--- a/basis/math/statistics/statistics.factor
+++ b/basis/math/statistics/statistics.factor
@@ -14,6 +14,9 @@ IN: math.statistics
 : harmonic-mean ( seq -- x )
     [ recip ] map-sum recip ;
 
+: contraharmonic-mean ( seq -- x )
+    [ [ sq ] map-sum ] [ sum ] bi / ;
+
 <PRIVATE
 
 :: ((kth-object)) ( seq k nth-quot exchange-quot quot: ( x y -- ? ) -- elt )