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math.extras: Add sum-cum-sum. Change concentration-coefficient to be more straightforward.

db4
Doug Coleman 2012-09-26 09:06:48 -07:00
parent 7fb8db2e74
commit 768611d130
1 changed files with 7 additions and 6 deletions
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13
extra/math/extras/extras.factor
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@ -155,14 +155,15 @@ PRIVATE>
: until-zero ( n quot -- ) : until-zero ( n quot -- )
[ dup zero? ] swap until drop ; inline [ dup zero? ] swap until drop ; inline
: sum-cum-sum ( seq -- sum sum-of-cumulative-sum-of-seq )
[ 0 0 ] dip [ '[ _ + ] dip dupd + ] each ; inline
<PRIVATE <PRIVATE
:: (gini) ( seq -- x ) :: (gini) ( seq -- x )
seq natural-sort :> sorted seq natural-sort :> sorted
seq length :> len seq length :> len
0 0 sorted [ sorted sum-cum-sum :> ( a b )
'[ _ + ] dip dupd +
] each :> ( a b )
b len a * / :> B b len a * / :> B
1 len recip + 2 B * - ; 1 len recip + 2 B * - ;
@ -172,8 +173,8 @@ PRIVATE>
dup length 1 <= [ drop 0 ] [ (gini) ] if ; dup length 1 <= [ drop 0 ] [ (gini) ] if ;
: concentration-coefficient ( seq -- x ) : concentration-coefficient ( seq -- x )
dup gini [ dup length 1 <= [
drop 0 drop 0
] [ ] [
[ length [ ] [ 1 - ] bi / ] dip * [ gini ] [ length [ ] [ 1 - ] bi / ] bi *
] if-zero ; ] if ;