math.statistics: faster and simpler entropy word.
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f019ee8776
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bdf02bfd2b
basis/math/statistics
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@ -330,8 +330,7 @@ ALIAS: corr sample-corr
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[ ?first ] keep [ max dup ] map nip ;
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[ ?first ] keep [ max dup ] map nip ;
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: entropy ( seq -- n )
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: entropy ( seq -- n )
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dup members [ [ = ] curry count ] with map
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histogram values dup sum '[ _ / dup log * ] map-sum neg ;
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dup sum v/n dup [ log ] map v* sum neg ;
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: binary-entropy ( p -- h )
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: binary-entropy ( p -- h )
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[ dup log * ] [ 1 swap - dup log * ] bi + neg 2 log / ;
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[ dup log * ] [ 1 swap - dup log * ] bi + neg 2 log / ;
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