1 ! Copyright (C) 2008 Doug Coleman, Michael Judge.
2 ! See http://factorcode.org/license.txt for BSD license.
3 USING: assocs combinators generalizations kernel locals math
4 math.functions math.order math.vectors sequences
5 sequences.private sorting ;
9 [ sum ] [ length ] bi / ;
11 : geometric-mean ( seq -- x )
12 [ length ] [ product ] bi nth-root ;
14 : harmonic-mean ( seq -- x )
15 [ recip ] map-sum recip ;
17 :: kth-smallest ( seq k -- elt )
18 #! Wirth's method, Algorithm's + Data structues = Programs p. 84
19 #! The algorithm modifiers seq, so we clone it
33 [ i seq nth-unsafe x < ] [ i 1 + i! ] while
34 [ x j seq nth-unsafe < ] [ j 1 - j! ] while
36 i j seq exchange-unsafe
47 : lower-median ( seq -- elt )
48 [ ] [ ] [ length odd? ] tri
49 [ midpoint@ ] [ midpoint@ 1 - ] if kth-smallest ;
51 : upper-median ( seq -- elt )
52 dup midpoint@ kth-smallest ;
54 : medians ( seq -- lower upper )
55 [ lower-median ] [ upper-median ] bi ;
58 [ ] [ length odd? ] bi [ lower-median ] [ medians + 2 / ] if ;
62 : (sequence>assoc) ( seq map-quot: ( x -- ..y ) insert-quot: ( ..y assoc -- ) assoc -- assoc )
63 [ swap curry compose each ] keep ; inline
67 : sequence>assoc! ( assoc seq map-quot: ( x -- ..y ) insert-quot: ( ..y assoc -- ) -- assoc )
68 4 nrot (sequence>assoc) ; inline
70 : sequence>assoc ( seq map-quot: ( x -- ..y ) insert-quot: ( ..y assoc -- ) exemplar -- assoc )
71 clone (sequence>assoc) ; inline
73 : sequence>hashtable ( seq map-quot: ( x -- ..y ) insert-quot: ( ..y assoc -- ) -- hashtable )
74 H{ } sequence>assoc ; inline
76 : histogram! ( hashtable seq -- hashtable )
77 [ ] [ inc-at ] sequence>assoc! ;
79 : histogram-by ( seq quot: ( x -- bin ) -- hashtable )
80 [ inc-at ] sequence>hashtable ; inline
82 : histogram ( seq -- hashtable )
85 : sorted-histogram ( seq -- alist )
86 histogram sort-values ;
88 : collect-pairs ( seq quot: ( x -- v k ) -- hashtable )
89 [ push-at ] sequence>hashtable ; inline
91 : collect-by ( seq quot: ( x -- x' ) -- hashtable )
92 [ dup ] prepose collect-pairs ; inline
96 [ ] [ [ [ second ] bi@ > ] most ] map-reduce first ;
98 ERROR: empty-sequence ;
100 : minmax ( seq -- min max )
104 [ first dup ] keep [ [ min ] [ max ] bi-curry bi* ] each
110 : sample-var ( seq -- x )
115 [ [ mean ] keep [ - sq ] with map-sum ]
123 [ [ mean ] keep [ - sq ] with map-sum ]
127 : std ( seq -- x ) var sqrt ;
129 : ste ( seq -- x ) [ std ] [ length ] bi sqrt / ;
131 : ((r)) ( mean(x) mean(y) {x} {y} -- (r) )
132 ! finds sigma((xi-mean(x))(yi-mean(y))
133 0 [ [ [ pick ] dip swap - ] bi@ * + ] 2reduce 2nip ;
135 : (r) ( mean(x) mean(y) {x} {y} sx sy -- r )
136 * recip [ [ ((r)) ] keep length 1 - / ] dip * ;
138 : [r] ( {{x,y}...} -- mean(x) mean(y) {x} {y} sx sy )
139 first2 [ [ [ mean ] bi@ ] 2keep ] 2keep [ std ] bi@ ;
141 : r ( {{x,y}...} -- r )
144 : r^2 ( {{x,y}...} -- r )
147 : least-squares ( {{x,y}...} -- alpha beta )
148 [r] { [ 2dup ] [ ] [ ] [ ] [ ] } spread
149 ! stack is mean(x) mean(y) mean(x) mean(y) {x} {y} sx sy
150 [ (r) ] 2keep ! stack is mean(x) mean(y) r sx sy
151 swap / * ! stack is mean(x) mean(y) beta
154 : cov ( {x} {y} -- cov )
155 [ dup mean v-n ] bi@ v* mean ;
157 : corr ( {x} {y} -- corr )
158 [ cov ] [ [ var ] bi@ * sqrt ] 2bi / ;