--- a/flys-artifacts/src/main/java/de/intevation/flys/artifacts/math/fitting/Linear.java	Wed May 30 17:59:19 2012 +0000
+++ b/flys-artifacts/src/main/java/de/intevation/flys/artifacts/math/fitting/Linear.java	Thu May 31 16:32:03 2012 +0000
@@ -3,6 +3,24 @@
 public class Linear
 extends      Function
 {
+    public static final Derivative DERIVATIVE =
+        new Derivative("W'(Q) = m") {
+
+        @Override
+        public de.intevation.flys.artifacts.math.Function
+            instantiate(double [] parameters)
+        {
+            final double m = parameters[0];
+
+            return new de.intevation.flys.artifacts.math.Function() {
+                @Override
+                public double value(double Q) {
+                    return m;
+                }
+            };
+        }
+    };
+
     public Linear() {
         super("linear", "W(Q) = m*Q + b", new String [] { "m", "b" });
     }
@@ -16,5 +34,10 @@
     public double [] gradient(double x, double [] parameters) {
         return new double [] { x, 1d };
     }
+
+    @Override
+    public Derivative getDerivative() {
+        return DERIVATIVE;
+    }
 }
 // vim:set ts=4 sw=4 si et sta sts=4 fenc=utf8 :