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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\Math\Comparison; |
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class DecisionTreeLeaf |
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{ |
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/** |
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* @var string|int |
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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|null |
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*/ |
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public $leftLeaf; |
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/** |
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* @var DecisionTreeLeaf|null |
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*/ |
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public $rightLeaf; |
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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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* HTML representation of the tree without column names |
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*/ |
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public function __toString(): string |
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{ |
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return $this->getHTML(); |
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} |
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public function evaluate(array $record): bool |
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{ |
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$recordField = $record[$this->columnIndex]; |
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if ($this->isContinuous) { |
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return Comparison::compare((string) $recordField, $this->numericValue, $this->operator); |
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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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public function getNodeImpurityDecrease(int $parentRecordCount): float |
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{ |
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if ($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 !== null) { |
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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 !== null) { |
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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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public function getHTML(?array $columnNames = null): string |
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{ |
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if ($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 ((bool) preg_match('/^[<>=]{1,2}/', (string) $value) === false) { |
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$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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$str = "<table ><tr><td colspan=3 align=center style='border:1px solid;'>${value}</td></tr>"; |
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if ($this->leftLeaf !== null || $this->rightLeaf !== null) { |
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$str .= '<tr>'; |
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if ($this->leftLeaf !== null) { |
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$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 ($this->rightLeaf !== null) { |
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$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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php-ai /
php-ml
