--- a/flys-artifacts/ChangeLog	Mon Jun 11 14:55:03 2012 +0000
+++ b/flys-artifacts/ChangeLog	Tue Jun 12 08:11:36 2012 +0000
@@ -1,3 +1,20 @@
+2012-06-11	Sascha L. Teichmann	<sascha.teichmann@intevation.de>
+
+	* src/main/java/de/intevation/flys/artifacts/model/Parameters.java:
+	  Added method double [] interpolate(keyName, key, columnNames).
+	  This construct is better suited for the extraction of
+	  coefficients for building functions. In pseudo code:
+
+	    fitting.Function function =
+		    FunctionFactory.getInstance().getFunction("log");
+
+	    double km = 42.35;
+
+	    double [] coeffs = parameters.interpolate(
+		    "km", km, function.getParamterNames());
+
+	    math.Function f = function.instantiate(coeffs);
+
 2012-06-11	Sascha L. Teichmann	<sascha.teichmann@intevation.de>
 
 	* src/main/java/de/intevation/flys/exports/fixings/FixWQCurveGenerator.java,

--- a/flys-artifacts/src/main/java/de/intevation/flys/artifacts/model/Parameters.java	Mon Jun 11 14:55:03 2012 +0000
+++ b/flys-artifacts/src/main/java/de/intevation/flys/artifacts/model/Parameters.java	Tue Jun 12 08:11:36 2012 +0000
@@ -177,8 +177,11 @@
         return interpolate(columnIndex(columnName), key, values);
     }
 
-    public double [] interpolate(int columnIndex, double key, double [] values) {
-
+    public double [] interpolate(
+        int       columnIndex, 
+        double    key, 
+        double [] values
+    ) {
         int row = binarySearch(columnIndex, key, EPSILON);
 
         if (row >= 0) {
@@ -204,6 +207,60 @@
         return values;
     }
 
+
+    public double [] interpolate(
+        String    keyName, 
+        double    key, 
+        String [] columnNames
+    ) {
+        int keyIndex = columnIndex(keyName);
+        return keyIndex < 0
+            ? null
+            : interpolate(keyIndex, key, columnNames);
+    }
+
+    public double [] interpolate(
+        int       keyIndex,
+        double    key,
+        String [] columnNames
+    ) {
+        int row = binarySearch(keyIndex, key, EPSILON);
+
+        if (row >= 0) { // direct match
+            double [] values = new double[columnNames.length];
+            for (int i = 0; i < values.length; ++i) {
+                int ci = columnIndex(columnNames[i]);
+                values[i] = ci < 0
+                    ? Double.NaN
+                    : columns[ci].getQuick(row);
+            }
+            return values;
+        }
+
+        row = -row - 1;
+        if (row < 1 || row >= size()) { // out of bounds
+            return null;
+        }
+
+        double v1 = columns[keyIndex].getQuick(row-1);
+        double v2 = columns[keyIndex].getQuick(row);
+        double factor = Linear.factor(key, v1, v2);
+
+        double [] values = new double[columnNames.length];
+
+        for (int i = 0; i < values.length; ++i) {
+            int ci = columnIndex(columnNames[i]);
+            values[i] = ci < 0
+                ? Double.NaN
+                : Linear.weight(
+                    factor,
+                    columns[ci].getQuick(row-1),
+                    columns[ci].getQuick(row));
+        }
+
+        return values;
+    }
+
     public boolean isSorted(String columnName) {
         return isSorted(columnIndex(columnName));
     }