From d5e26ee76dc8cbae13f4ab6a825b3f2ca4f4d308 Mon Sep 17 00:00:00 2001
From: Doug Coleman <doug.coleman@gmail.com>
Date: Tue, 25 Sep 2012 17:52:27 -0700
Subject: [PATCH] math.extras: Faster gini. Leaving this as a separate patch
for comparison.
---
extra/math/extras/extras.factor | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/extra/math/extras/extras.factor b/extra/math/extras/extras.factor
index 005a924453..550484dd89 100644
--- a/extra/math/extras/extras.factor
+++ b/extra/math/extras/extras.factor
@@ -4,7 +4,7 @@
USING: combinators.short-circuit grouping kernel locals math
math.combinatorics math.constants math.functions math.order
math.primes math.ranges math.statistics math.vectors memoize
-sequences sequences.extras sorting assocs ;
+sequences sequences.extras sorting assocs fry ;
IN: math.extras
@@ -160,9 +160,11 @@ PRIVATE>
:: (gini) ( seq -- x )
seq natural-sort :> sorted
seq length :> len
- len [1,b] sorted zip 0 [ * + ] assoc-reduce :> sum0
- 2 sum0 * sorted sum len * / :> G
- G 1 - 1 len / - ; inline
+ 0 0 sorted [
+ '[ _ + ] dip dupd +
+ ] each :> ( a b )
+ b len a * / :> B
+ 1 len recip + 2 B * - ;
PRIVATE>