--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/artifacts/src/main/java/org/dive4elements/river/artifacts/sinfo/util/LinearInterpolator.java	Thu Mar 29 15:48:17 2018 +0200
@@ -0,0 +1,77 @@
+/** Copyright (C) 2017 by Bundesanstalt für Gewässerkunde
+ * Software engineering by
+ *  Björnsen Beratende Ingenieure GmbH
+ *  Dr. Schumacher Ingenieurbüro für Wasser und Umwelt
+ *
+ * This file is Free Software under the GNU AGPL (>=v3)
+ * and comes with ABSOLUTELY NO WARRANTY! Check out the
+ * documentation coming with Dive4Elements River for details.
+ */
+package org.dive4elements.river.artifacts.sinfo.util;
+
+import java.util.Map.Entry;
+import java.util.NavigableMap;
+import java.util.TreeMap;
+
+import org.dive4elements.river.artifacts.math.Linear;
+import org.dive4elements.river.artifacts.model.Calculation;
+
+import gnu.trove.TDoubleArrayList;
+
+/**
+ * Helper for interpolating values from a piecewise linear function defined by discrete values.
+ *
+ * @author Gernot Belger
+ */
+public final class LinearInterpolator {
+
+    private final NavigableMap<Double, Double> data;
+    private final double maxDistance;
+
+    private Calculation problems;
+
+    public static LinearInterpolator create(final Calculation problems, final TDoubleArrayList xs, final TDoubleArrayList ys, final double maxDistance) {
+        if (xs.size() != ys.size())
+            throw new IllegalArgumentException("Array sizes must be equal");
+
+        if (xs.size() < 2)
+            throw new IllegalArgumentException("Array must have at least 2 values");
+
+        final NavigableMap<Double, Double> data = new TreeMap<>();
+
+        for (int i = 0; i < xs.size(); i++) {
+            final double x = xs.getQuick(i);
+            final double y = ys.getQuick(i);
+            data.put(x, y);
+        }
+
+        return new LinearInterpolator(problems, data, maxDistance);
+    }
+
+    private LinearInterpolator(final Calculation problems, final NavigableMap<Double, Double> data, final double maxDistance) {
+        this.problems = problems;
+        this.data = data;
+        this.maxDistance = maxDistance;
+    }
+
+    public double value(final double value) {
+
+        final Entry<Double, Double> floorEntry = this.data.floorEntry(value);
+        final Entry<Double, Double> ceilingEntry = this.data.ceilingEntry(value);
+
+        if (floorEntry == null || ceilingEntry == null)
+            return Double.NaN;
+
+        final double floorKey = floorEntry.getKey();
+        final double floorValue = floorEntry.getValue();
+        final double ceilingKey = ceilingEntry.getKey();
+        final double ceilingValue = ceilingEntry.getValue();
+
+        if (Math.abs(floorKey - ceilingKey) > this.maxDistance && this.problems != null) {
+            this.problems.addProblem(value, "linearInterpolator.maxdistance", this.maxDistance * 1000);
+            this.problems = null;
+        }
+
+        return Linear.linear(value, floorKey, ceilingKey, floorValue, ceilingValue);
+    }
+}
\ No newline at end of file