40 lines
945 B
Factor
40 lines
945 B
Factor
IN: math-contrib
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USING: kernel math sequences ;
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: mean ( seq -- n )
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#! arithmetic mean, sum divided by length
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[ sum ] keep length / ;
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: geometric-mean ( seq -- n )
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#! geometric mean, nth root of product
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[ product ] keep length swap nth-root ;
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: harmonic-mean ( seq -- n )
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#! harmonic mean, reciprocal of sum of reciprocals.
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#! positive reals only
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0 [ recip + ] reduce recip ;
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: median ( seq -- n )
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#! middle number if odd, avg of two middle numbers if even
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natural-sort dup length dup even? [
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1- 2 / swap [ nth ] 2keep >r 1+ r> nth + 2 /
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] [
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2 / swap nth
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] if ;
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: range ( seq -- n )
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#! max - min
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minmax swap - ;
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: var ( seq -- x )
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#! variance, normalize by N-1
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dup length 1- dup zero? [
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0 2nip
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] [
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swap [ mean ] keep 0 [ pick - sq + ] reduce nip swap /
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] if ;
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: std ( seq -- x )
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#! standard deviation, sqrt of variance
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var sqrt ;
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