33 lines
1.0 KiB
Haskell
33 lines
1.0 KiB
Haskell
module ExtractRules (
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extractRules
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) where
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import DataModel
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import qualified Data.Set as Set
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import qualified Data.Map as Map
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import Data.Map(Map)
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extractRules :: Confidence -> [ItemSet] -> [Rule]
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extractRules threshold patterns = filter (\x -> threshold <= confidence patterns x) rules where
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rules = Map.foldrWithKey (\k v old -> ruleFromSubset v k : old) [] subsets
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subsets = foldr (\x old -> insertMultiple (filteredPowerset x) x old) Map.empty patterns
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filteredPowerset (ItemSet set) = map (ItemSet . Set.fromList) $
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filter (\val -> val /= Set.toList set && val /= []) $ powerset $ Set.toList set
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ruleFromSubset :: ItemSet -> ItemSet -> Rule
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ruleFromSubset set subset = Rule subset (difference set subset)
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insertMultiple :: Ord k => [k] -> a -> Map k a -> Map k a
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insertMultiple keys value m = foldr (\x old -> Map.insert x value old) m keys
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powerset :: [a] -> [[a]]
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powerset [] = [[]]
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powerset (x:xs) = xss /\/ map (x:) xss where
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xss = powerset xs
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(/\/) :: [a] -> [a] -> [a]
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[] /\/ ys = ys
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(x:xs) /\/ ys = x : (ys /\/ xs)
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