feat:node-modules

node_modules/complex.js/examples/gamma.js

@@ -0,0 +1,33 @@
+/*
+ * A gamma function implementation based on Lanczos Approximation
+ * https://en.wikipedia.org/wiki/Lanczos_approximation
+ */
+
+var Complex = require('complex.js');
+
+var P = [
+  Complex(0.99999999999980993),
+  Complex(676.5203681218851), Complex(-1259.1392167224028), Complex(771.32342877765313),
+  Complex(-176.61502916214059), Complex(12.507343278686905), Complex(-0.13857109526572012),
+  Complex(9.9843695780195716e-6), Complex(1.5056327351493116e-7)
+];
+
+var SQRT2PI = Complex(Math.sqrt(2 * Math.PI));
+
+function gamma(z) {
+
+  z = z.sub(1);
+
+  var x = P[0];
+  var t = z.add(7.5);
+  for (var i = 1; i < P.length; i++) {
+    x = x.add(P[i].div(z.add(i)));
+  }
+  return SQRT2PI.mul(t.pow(z.add(0.5))).mul(t.neg().exp()).mul(x);
+}
+
+var fac = 1;
+for (var i = 1; i <= 10; i++) {
+  console.log(fac, gamma(Complex(i)));
+  fac *= i;
+}