Merge pull request #7 from integer-net/max-len

Add configuration to limit length of rules

Author: schmengler

src/FPGrowth.php

@@ -10,6 +10,7 @@ class FPGrowth
 {
     protected int $support = 3;
     protected float $confidence = 0.7;
+    private int $maxLength = 0;
 
     private $patterns;
     private $rules;
@@ -50,6 +51,15 @@ public function setConfidence(float $confidence): self
         return $this;
     }
 
+    public function getMaxLength(): int
+    {
+        return $this->maxLength;
+    }
+
+    public function setMaxLength(int $maxLength): void
+    {
+        $this->maxLength = $maxLength;
+    }
     /**
      * @return mixed
      */
@@ -71,10 +81,11 @@ public function getRules()
      * @param int $support 1, 2, 3 ...
      * @param float $confidence 0 ... 1
      */
-    public function __construct(int $support, float $confidence)
+    public function __construct(int $support, float $confidence, int $maxLength = 0)
     {
         $this->setSupport($support);
         $this->setConfidence($confidence);
+        $this->setMaxLength($maxLength);
     }
 
     /**
@@ -93,7 +104,7 @@ public function run(array $transactions)
      */
     protected function findFrequentPatterns(array $transactions): array
     {
-        $tree = new FPTree($transactions, $this->support, null, 0);
+        $tree = new FPTree($transactions, $this->support, null, 0, $this->maxLength);
         return $tree->minePatterns($this->support);
     }
 

src/FPTree.php

@@ -16,18 +16,23 @@ class FPTree
 
     private FPNode $root;
 
+    private int $maxLength = 0;
+
+    private int $depth = 0;
+
     /**
      * Initialize the tree.
      * @param array $transactions
      * @param int $threshold
      * @param $rootValue
      * @param int $rootCount
      */
-    public function __construct(array $transactions, int $threshold, $rootValue, int $rootCount)
+    public function __construct(array $transactions, int $threshold, $rootValue, int $rootCount, $maxLength = 0)
     {
         $this->frequent = $this->findFrequentItems($transactions, $threshold);
         $this->headers = $this->buildHeaderTable();
         $this->root = $this->buildFPTree($transactions, $rootValue, $rootCount, $this->frequent);
+        $this->maxLength = $maxLength;
     }
 
     /**
@@ -168,6 +173,8 @@ public function minePatterns(int $threshold): array
     {
         if ($this->treeHasSinglePath($this->root)) {
             return $this->generatePatternList();
+        } elseif ($this->maxLength && $this->maxLength <= $this->getDepth()) {
+            return [];
         }
 
         return $this->zipPatterns($this->mineSubTrees($threshold));
@@ -211,7 +218,13 @@ protected function generatePatternList(): array
             $patterns[$this->root->value] = $this->root->count;
         }
 
-        for ($i = 1; $i <= count($items); $i++) {
+        // limit length of combinations to remaining length
+        $count = count($items);
+        if ($this->maxLength) {
+            $count = min($count, $this->maxLength - $this->getDepth());
+        }
+
+        for ($i = 1; $i <= $count; $i++) {
             $combinations = new Combinations($items,$i);
             foreach ($combinations->generator() as $subset) {
                 $pattern = $this->root->value !== null ? array_merge($subset, [$this->root->value]) : $subset;
@@ -270,7 +283,8 @@ protected function mineSubTrees(int $threshold): array
             }
 
             // Now we have the input for a subtree, so construct it and grab the patterns.
-            $subtree = new FPTree($conditionalTreeInput, $threshold, $item, $this->frequent[$item]);
+            $subtree = new FPTree($conditionalTreeInput, $threshold, $item, $this->frequent[$item], $this->maxLength);
+            $subtree->depth = $this->depth + 1;
             $subtreePatterns = $subtree->minePatterns($threshold);
 
             // Insert subtree patterns into main patterns dictionary.
@@ -285,4 +299,9 @@ protected function mineSubTrees(int $threshold): array
 
         return $patterns;
     }
+
+    private function getDepth(): int
+    {
+        return $this->depth;
+    }
 }