implemented phase 2

ExtractRules.hs

@@ -0,0 +1,32 @@
+module ExtractRules (
+    extractRules
+) where
+import DataModel
+import qualified Data.Set as Set
+import qualified Data.Map as Map
+import Data.Map(Map)
+
+extractRules :: Confidence -> [ItemSet] -> [Rule]
+extractRules threshold patterns = filter (\x -> threshold <= confidence patterns x) rules where
+    rules = Map.foldrWithKey (\k v old -> ruleFromSubset v k : old) [] subsets
+    subsets = foldr (\x old -> insertMultiple (filteredPowerset x) x old) Map.empty patterns
+    filteredPowerset (ItemSet set) = map (ItemSet . Set.fromList) $
+        filter (\val -> val /= Set.toList set && val /= []) $ powerset $ Set.toList set
+
+ruleFromSubset :: ItemSet -> ItemSet -> Rule
+ruleFromSubset set subset = Rule subset (difference set subset)
+
+
+
+insertMultiple :: Ord k => [k] -> a -> Map k a -> Map k a
+insertMultiple keys value m = foldr (\x old -> Map.insert x value old) m keys
+
+powerset :: [a] -> [[a]]
+powerset []     = [[]]
+powerset (x:xs) = xss /\/ map (x:) xss where
+    xss = powerset xs
+
+(/\/) :: [a] -> [a] -> [a]
+[]     /\/ ys = ys
+(x:xs) /\/ ys = x : (ys /\/ xs)
+