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<?php |
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declare(strict_types=1); |
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namespace Phpml\Classification\DecisionTree; |
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use Phpml\Exception\InvalidArgumentException; |
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class DecisionTreeLeaf |
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{ |
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/** |
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* @var string |
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*/ |
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public $value; |
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/** |
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* @var float |
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*/ |
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public $numericValue; |
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/** |
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* @var string |
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*/ |
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public $operator; |
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/** |
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* @var int |
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*/ |
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public $columnIndex; |
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/** |
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* @var DecisionTreeLeaf |
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*/ |
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public $leftLeaf = null; |
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/** |
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* @var DecisionTreeLeaf |
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*/ |
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public $rightLeaf= null; |
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/** |
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* @var array |
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*/ |
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public $records = []; |
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/** |
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* Class value represented by the leaf, this value is non-empty |
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* only for terminal leaves |
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* |
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* @var string |
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*/ |
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public $classValue = ''; |
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/** |
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* @var bool |
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*/ |
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public $isTerminal = false; |
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/** |
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* @var bool |
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*/ |
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public $isContinuous = false; |
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/** |
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* @var float |
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*/ |
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public $giniIndex = 0; |
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/** |
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* @var int |
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*/ |
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public $level = 0; |
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/** |
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* @param array $record |
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* @return bool |
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* @throws InvalidArgumentException |
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*/ |
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public function evaluate($record) |
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{ |
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$recordField = $record[$this->columnIndex]; |
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if ($this->isContinuous) { |
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$op = $this->operator; |
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$value = $this->numericValue; |
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if (is_null($recordField)) { |
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return false; |
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} |
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$recordField = strval($recordField); |
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switch ($op) { |
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case '>=': |
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return ($recordField >= $value); |
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case '<=': |
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return ($recordField <= $value); |
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case '>': |
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return ($recordField > $value); |
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case '<': |
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return ($recordField < $value); |
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case '==': |
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case '=': |
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return ($recordField == $value); |
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default: |
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throw new InvalidArgumentException('Malformed operator: '.$op); |
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} |
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} |
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return $recordField == $this->value; |
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} |
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/** |
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* Returns Mean Decrease Impurity (MDI) in the node. |
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* For terminal nodes, this value is equal to 0 |
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* |
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* @param int $parentRecordCount |
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* |
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* @return float |
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*/ |
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public function getNodeImpurityDecrease(int $parentRecordCount) |
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{ |
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if ($this->isTerminal) { |
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return 0.0; |
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} |
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$nodeSampleCount = (float)count($this->records); |
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$iT = $this->giniIndex; |
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if ($this->leftLeaf) { |
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$pL = count($this->leftLeaf->records)/$nodeSampleCount; |
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$iT -= $pL * $this->leftLeaf->giniIndex; |
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} |
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if ($this->rightLeaf) { |
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$pR = count($this->rightLeaf->records)/$nodeSampleCount; |
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$iT -= $pR * $this->rightLeaf->giniIndex; |
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} |
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return $iT * $nodeSampleCount / $parentRecordCount; |
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} |
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/** |
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* Returns HTML representation of the node including children nodes |
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* |
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* @param $columnNames |
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* @return string |
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*/ |
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public function getHTML($columnNames = null) |
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{ |
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if ($this->isTerminal) { |
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$value = "<b>$this->classValue</b>"; |
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} else { |
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$value = $this->value; |
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if ($columnNames !== null) { |
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$col = $columnNames[$this->columnIndex]; |
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} else { |
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$col = "col_$this->columnIndex"; |
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} |
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if (!preg_match("/^[<>=]{1,2}/", $value)) { |
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$value = "=$value"; |
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} |
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$value = "<b>$col $value</b><br>Gini: ". number_format($this->giniIndex, 2); |
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} |
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$str = "<table ><tr><td colspan=3 align=center style='border:1px solid;'> |
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$value</td></tr>"; |
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if ($this->leftLeaf || $this->rightLeaf) { |
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$str .='<tr>'; |
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if ($this->leftLeaf) { |
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$str .="<td valign=top><b>| Yes</b><br>" . $this->leftLeaf->getHTML($columnNames) . "</td>"; |
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} else { |
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$str .='<td></td>'; |
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} |
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$str .='<td> </td>'; |
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if ($this->rightLeaf) { |
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$str .="<td valign=top align=right><b>No |</b><br>" . $this->rightLeaf->getHTML($columnNames) . "</td>"; |
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} else { |
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$str .='<td></td>'; |
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} |
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$str .= '</tr>'; |
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} |
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$str .= '</table>'; |
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return $str; |
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} |
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/** |
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* HTML representation of the tree without column names |
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* |
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* @return string |
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*/ |
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public function __toString() |
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{ |
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return $this->getHTML(); |
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} |
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} |
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php-ai /
php-ml
