--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/artifacts/src/main/java/org/dive4elements/river/artifacts/math/fitting/SQPow.java	Thu Apr 25 15:23:37 2013 +0200
@@ -0,0 +1,60 @@
+package org.dive4elements.river.artifacts.math.fitting;
+
+public class SQPow
+extends      Function
+{
+    public static final Derivative DERIVATIVE =
+        new Derivative("S'(Q) = a*b*Q^(b-1)") {
+
+        @Override
+        public org.dive4elements.river.artifacts.math.Function
+            instantiate(double [] parameters)
+        {
+            final double a = parameters[0];
+            final double b = parameters[1];
+
+            return new org.dive4elements.river.artifacts.math.Function() {
+                @Override
+                public double value(double Q) {
+                    return a*b*Math.pow(Q, b-1);
+                }
+            };
+        }
+    };
+
+    public static final Function INSTANCE = new SQPow();
+
+    public SQPow() {
+        super(
+            "sq-pow",
+            "S(Q) = a*Q^b",
+            new String [] { "a", "b" });
+    }
+
+    @Override
+    public double value(double x, double [] parameters) {
+        return parameters[0]*Math.pow(x, parameters[1]);
+    }
+
+    @Override
+    public double [] gradient(double q, double [] parameters) {
+        double a   = parameters[0];
+        double b   = parameters[1];
+        double q_b = Math.pow(q, b);
+        return new double [] {
+            q_b,
+            a*q_b*Math.log(q),
+        };
+    }
+
+    @Override
+    public Derivative getDerivative() {
+        return DERIVATIVE;
+    }
+
+    @Override
+    public Function getInverse() {
+        return InvSQPow.INSTANCE;
+    }
+}
+// vim:set ts=4 sw=4 si et sta sts=4 fenc=utf8 :