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math.statistics: Generalize kth-smallest into kth-object, add kth-largest. Add count-relative and minmax-relative for counting the number of lt, eq, gt elements, and getting the max lt and min gt in one pass.

db4
Doug Coleman 2012-04-22 23:41:13 -07:00
parent c00ddde434
commit 7ad089b682
2 changed files with 32 additions and 4 deletions
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6
basis/math/statistics/statistics-tests.factor
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@ -13,6 +13,12 @@ IN: math.statistics.tests
[ 2 ] [ { 1 2 3 } median ] unit-test
[ 5/2 ] [ { 1 2 3 4 } median ] unit-test
{ 1 } [ { 1 2 3 4 } 0 kth-smallest ] unit-test
{ 3 } [ { 1 2 3 4 } 2 kth-smallest ] unit-test
{ 4 } [ { 1 2 3 4 } 0 kth-largest ] unit-test
{ 2 } [ { 1 2 3 4 } 2 kth-largest ] unit-test
[ 1 ] [ { 1 } mode ] unit-test
[ 3 ] [ { 1 2 3 3 3 4 5 6 76 7 2 21 1 3 3 3 } mode ] unit-test

30
basis/math/statistics/statistics.factor
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@ -2,7 +2,7 @@
! See http://factorcode.org/license.txt for BSD license.
USING: assocs combinators generalizations kernel locals math
math.functions math.order math.vectors sequences
sequences.private sorting ;
sequences.private sorting fry ;
IN: math.statistics
: mean ( seq -- x )
@ -14,7 +14,7 @@ IN: math.statistics
: harmonic-mean ( seq -- x )
[ recip ] map-sum recip ;
:: kth-smallest ( seq k -- elt )
:: kth-object ( seq k quot: ( x y -- ? ) -- elt )
#! Wirth's method, Algorithm's + Data structues = Programs p. 84
#! The algorithm modifiers seq, so we clone it
seq clone :> seq
@ -30,8 +30,8 @@ IN: math.statistics
m j!
[ i j <= ]
[
[ i seq nth-unsafe x < ] [ i 1 + i! ] while
[ x j seq nth-unsafe < ] [ j 1 - j! ] while
[ i seq nth-unsafe x quot call ] [ i 1 + i! ] while
[ x j seq nth-unsafe quot call ] [ j 1 - j! ] while
i j <= [
i j seq exchange-unsafe
i 1 + i!
@ -44,6 +44,28 @@ IN: math.statistics
] while
k seq nth ; inline
: kth-smallest ( seq k -- elt ) [ < ] kth-object ;
: kth-largest ( seq k -- elt ) [ > ] kth-object ;
: count-relative ( seq k -- lt eq gt )
[ 0 0 0 ] 2dip '[
_ <=> {
{ +lt+ [ [ 1 + ] 2dip ] }
{ +gt+ [ 1 + ] }
{ +eq+ [ [ 1 + ] dip ] }
} case
] each ;
: minmax-relative ( seq k -- lt eq gt lt-max gt-min )
[ 0 0 0 -1/0. 1/0. ] 2dip '[
dup _ <=> {
{ +lt+ [ [ 1 + ] 5 ndip '[ _ max ] dip ] }
{ +gt+ [ [ 1 + ] 3dip min ] }
{ +eq+ [ [ 1 + ] 4dip drop ] }
} case
] each ;
: lower-median ( seq -- elt )
[ ] [ ] [ length odd? ] tri
[ midpoint@ ] [ midpoint@ 1 - ] if kth-smallest ;