--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/flys-artifacts/src/main/java/org/dive4elements/river/artifacts/math/fitting/Pow.java	Thu Apr 25 12:06:39 2013 +0200
@@ -0,0 +1,61 @@
+package org.dive4elements.river.artifacts.math.fitting;
+
+public class Pow
+extends      Function
+{
+    public static final Derivative DERIVATIVE =
+        new Derivative("W'(Q) = a*c*Q^(c-1)") {
+
+        @Override
+        public org.dive4elements.river.artifacts.math.Function
+            instantiate(double [] parameters)
+        {
+            final double a = parameters[0];
+            final double c = parameters[1];
+
+            return new org.dive4elements.river.artifacts.math.Function() {
+                @Override
+                public double value(double Q) {
+                    return a*c*Math.pow(Q, c-1);
+                }
+            };
+        }
+    };
+
+    public static final Function INSTANCE = new Pow();
+
+    public Pow() {
+        super(
+            "pow",
+            "W(Q) = a*Q^c + d",
+            new String [] { "a", "c", "d" });
+    }
+
+    @Override
+    public double value(double x, double [] parameters) {
+        return parameters[0]*Math.pow(x, parameters[1]) + parameters[2];
+    }
+
+    @Override
+    public double [] gradient(double x, double [] parameters) {
+        double a   = parameters[0];
+        double c   = parameters[1];
+        double x_c = Math.pow(x, c);
+        return new double [] {
+            x_c,
+            a*x_c*Math.log(x),
+            1d
+        };
+    }
+
+    @Override
+    public Derivative getDerivative() {
+        return DERIVATIVE;
+    }
+
+    @Override
+    public Function getInverse() {
+        return InvPow.INSTANCE;
+    }
+}
+// vim:set ts=4 sw=4 si et sta sts=4 fenc=utf8 :