43 lines
1.3 KiB
Factor
43 lines
1.3 KiB
Factor
! Copyright (C) 2012 Doug Coleman.
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! See http://factorcode.org/license.txt for BSD license.
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USING: arrays assocs fry kernel math math.functions
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math.statistics memoize random sequences sorting ;
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IN: machine-learning.rebalancing
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ERROR: probability-sum-not-one seq ;
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: check-probabilities ( seq -- seq )
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dup sum 1.0 .00000000001 ~ [ probability-sum-not-one ] unless ;
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: equal-probabilities ( n -- array )
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dup recip <array> ; inline
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MEMO: probabilities-seq ( seq -- seq' )
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check-probabilities [ >float ] map cum-sum ;
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: probabilities-quot ( seq -- quot )
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probabilities-seq
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'[ _ random-unit '[ _ > ] find drop ] ; inline
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: stratified-sample ( stratified-sequences probability-sequence -- elt )
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probabilities-quot call swap nth random ; inline
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: balance-labels ( X y n -- X' y' )
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[
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dup [ ] collect-index-by
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values dup length equal-probabilities
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'[
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_ _ _ _ stratified-sample
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'[ _ swap nth ] bi@ 2array
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]
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] dip swap replicate [ keys ] [ values ] bi ;
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: skew-labels ( X y probs n -- X' y' )
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[
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[ dup [ ] collect-index-by sort-keys values ] dip
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'[
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_ _ _ _ stratified-sample
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'[ _ swap nth ] bi@ 2array
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]
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] dip swap replicate [ keys ] [ values ] bi ;
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