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+<?php
+
+require_once "../Matrix.php";
+
+/**
+ * Given n points (x0,y0)...(xn-1,yn-1), the following method computes
+ * the polynomial factors of the n-1't degree polynomial passing through
+ * the n points.
+ *
+ * Example: Passing in three points (2,3) (1,4) and (3,7) will produce
+ * the results [2.5, -8.5, 10] which means that the points are on the
+ * curve y = 2.5x² - 8.5x + 10.
+ *
+ * @see http://geosoft.no/software/lagrange/LagrangeInterpolation.java.html
+ * @see http://source.freehep.org/jcvsweb/ilc/LCSIM/wdview/lcsim/src/org/lcsim/fit/polynomial/PolynomialFitter.java
+ * @author Jacob Dreyer
+ * @author Paul Meagher (port to PHP and minor changes)
+ *
+ * @param x[] float
+ * @param y[] float
+ */
+class LagrangeInterpolation {
+
+	public function findPolynomialFactors($x, $y) {
+		$n = count($x);
+
+		$data = array();  // double[n][n];
+		$rhs  = array();  // double[n];
+
+		for ($i = 0; $i < $n; ++$i) {
+			$v = 1;
+			for ($j = 0; $j < $n; ++$j) {
+				$data[$i][$n-$j-1] = $v;
+				$v *= $x[$i];
+			}
+			$rhs[$i] = $y[$i];
+		}
+
+		// Solve m * s = b
+		$m = new Matrix($data);
+		$b = new Matrix($rhs, $n);
+
+		$s = $m->solve($b);
+
+		return $s->getRowPackedCopy();
+	}	//	function findPolynomialFactors()
+
+}	//	class LagrangeInterpolation
+
+
+$x = array(2.0, 1.0, 3.0);
+$y = array(3.0, 4.0, 7.0);
+
+$li = new LagrangeInterpolation;
+$f = $li->findPolynomialFactors($x, $y);
+
+for ($i = 0; $i < 3; ++$i) {
+	echo $f[$i]."<br />";
+}