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Merge branch 'master' of git://factorcode.org/git/factor

db4
Doug Coleman 2008-09-22 21:34:22 -05:00
parent c2bcd893ef c689ef53d8
commit 0240427ab3
1 changed files with 4 additions and 4 deletions
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8
extra/math/statistics/statistics.factor
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@ -4,21 +4,21 @@ IN: math.statistics
: mean ( seq -- n )
#! arithmetic mean, sum divided by length
[ sum ] keep length / ;
[ sum ] [ length ] bi / ;
: geometric-mean ( seq -- n )
#! geometric mean, nth root of product
[ product ] keep length swap nth-root ;
[ length ] [ product ] bi nth-root ;
: harmonic-mean ( seq -- n )
#! harmonic mean, reciprocal of sum of reciprocals.
#! positive reals only
0 [ recip + ] reduce recip ;
[ recip ] sigma recip ;
: median ( seq -- n )
#! middle number if odd, avg of two middle numbers if even
natural-sort dup length dup even? [
1- 2 / swap [ nth ] 2keep >r 1+ r> nth + 2 /
1- 2 / swap [ nth ] [ >r 1+ r> nth ] 2bi + 2 /
] [
2 / swap nth
] if ;