ChartWindow: Make gebunden type fixed more user friendly

Elwig/Helpers/Billing/Graph.cs

@@ -28,6 +28,14 @@ namespace Elwig.Helpers.Billing {
             DataY = DataX.Select(i => (double)BillingData.GetCurveValueAt(data, i)).ToArray();
         }
 
+        public Graph(double[] values, int precision, int minX, int maxX) {
+            Precision = precision;
+            MinX = minX;
+            MaxX = maxX;
+            DataX = Enumerable.Range(MinX, MaxX - MinX + 1).Select(i => (double)i).ToArray();
+            DataY = values;
+        }
+
         private Graph(double[] dataX, double[] dataY, int precision, int minX, int maxX) {
             Precision = precision;
             MinX = minX;
@@ -52,6 +60,10 @@ namespace Elwig.Helpers.Billing {
             return DataY[index];
         }
 
+        public double GetPriceAtOe(double oe) {
+            return DataY[Array.IndexOf(DataX, oe)];
+        }
+
         private void FlattenGraph(int begin, int end, double value) {
             for (int i = begin; i <= end; i++) {
                 DataY[i] = value;