--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/artifacts/src/main/java/org/dive4elements/river/artifacts/model/DifferenceCurveFilterFacet.java	Thu Mar 06 14:04:46 2014 +0100
@@ -0,0 +1,82 @@
+package org.dive4elements.river.artifacts.model;
+
+import org.apache.log4j.Logger;
+import org.dive4elements.artifactdatabase.state.Facet;
+import org.dive4elements.artifacts.Artifact;
+import org.dive4elements.artifacts.CallContext;
+import org.dive4elements.river.artifacts.D4EArtifact;
+import org.dive4elements.river.artifacts.WINFOArtifact;
+import org.dive4elements.river.artifacts.access.RiverAccess;
+import org.dive4elements.river.artifacts.context.RiverContext;
+import org.dive4elements.river.artifacts.math.MovingAverage;
+import org.dive4elements.river.artifacts.states.DefaultState.ComputeType;
+
+
+public class DifferenceCurveFilterFacet
+extends DifferenceCurveFacet
+{
+    private static Logger logger = Logger.getLogger(DifferenceCurveFacet.class);
+
+
+    public DifferenceCurveFilterFacet() {
+    }
+
+    public DifferenceCurveFilterFacet(
+        int         index,
+        String      name,
+        String      description,
+        ComputeType type,
+        String      stateID,
+        String      hash
+
+    ) {
+        super(index, name, description, type, stateID, hash);
+    }
+
+    /**
+     * Get difference curve data.
+     * @return a WKms at given index.
+     */
+    @Override
+    public Object getData(Artifact artifact, CallContext context) {
+        WKms result = (WKms)super.getData(artifact, context);
+
+        Double start = (Double)context.getContextValue("startkm");
+        Double end = (Double)context.getContextValue("endkm");
+        if(start != null && end != null) {
+            RiverContext fc = (RiverContext)context.globalContext();
+            // Adaptive smoothing, based on zoom factor/diagram extents.
+            ZoomScale scales = (ZoomScale)fc.get("zoomscale");
+            RiverAccess access = new RiverAccess((D4EArtifact)artifact);
+            String river = access.getRiverName();
+
+            double radius = scales.getRadius(river, start, end);
+
+            double[][] oldData = new double[2][result.size()];
+            for (int i = 0; i < result.size(); i++) {
+                oldData[0][i] = result.getKm(i);
+                oldData[1][i] = result.getW(i);
+            }
+
+            double[][] diffs = MovingAverage.weighted(oldData, radius);
+            WKmsImpl newData = new WKmsImpl();
+            for(int j = 0; j < diffs[0].length; j++) {
+                newData.add(diffs[0][j], diffs[1][j]);
+            }
+            return newData;
+        }
+        return result;
+    }
+
+
+    /** Copy deeply. */
+    @Override
+    public Facet deepCopy() {
+        WaterlevelFacet copy = new DifferenceCurveFilterFacet();
+        copy.set(this);
+        copy.type    = type;
+        copy.stateId = stateId;
+        copy.hash    = hash;
+        return copy;
+    }
+}