Index: stable/HeuristicLab.Problems.DataAnalysis.Symbolic/3.4/Formatters/SymbolicDataAnalysisExpressionExcelFormatter.cs
===================================================================
--- stable/HeuristicLab.Problems.DataAnalysis.Symbolic/3.4/Formatters/SymbolicDataAnalysisExpressionExcelFormatter.cs	(revision 9931)
+++ stable/HeuristicLab.Problems.DataAnalysis.Symbolic/3.4/Formatters/SymbolicDataAnalysisExpressionExcelFormatter.cs	(revision 9931)
@@ -0,0 +1,211 @@
+﻿#region License Information
+/* HeuristicLab
+ * Copyright (C) 2002-2013 Heuristic and Evolutionary Algorithms Laboratory (HEAL)
+ *
+ * This file is part of HeuristicLab.
+ *
+ * HeuristicLab is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * HeuristicLab is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with HeuristicLab. If not, see <http://www.gnu.org/licenses/>.
+ */
+#endregion
+
+using System;
+using System.Collections.Generic;
+using System.Globalization;
+using System.Linq;
+using System.Text;
+using HeuristicLab.Common;
+using HeuristicLab.Core;
+using HeuristicLab.Encodings.SymbolicExpressionTreeEncoding;
+using HeuristicLab.Persistence.Default.CompositeSerializers.Storable;
+
+namespace HeuristicLab.Problems.DataAnalysis.Symbolic {
+  [Item("Excel String Formatter", "String formatter for string representations of symbolic data analysis expressions in Excel syntax.")]
+  [StorableClass]
+  public sealed class SymbolicDataAnalysisExpressionExcelFormatter : NamedItem, ISymbolicExpressionTreeStringFormatter {
+    [StorableConstructor]
+    private SymbolicDataAnalysisExpressionExcelFormatter(bool deserializing) : base(deserializing) { }
+    private SymbolicDataAnalysisExpressionExcelFormatter(SymbolicDataAnalysisExpressionExcelFormatter original, Cloner cloner) : base(original, cloner) { }
+    public SymbolicDataAnalysisExpressionExcelFormatter()
+      : base() {
+      Name = ItemName;
+      Description = ItemDescription;
+    }
+    public override IDeepCloneable Clone(Cloner cloner) {
+      return new SymbolicDataAnalysisExpressionExcelFormatter(this, cloner);
+    }
+    private string GetExcelColumnName(int columnNumber) {
+      int dividend = columnNumber;
+      string columnName = String.Empty;
+
+      while (dividend > 0) {
+        int modulo = (dividend - 1) % 26;
+        columnName = Convert.ToChar(65 + modulo).ToString() + columnName;
+        dividend = (int)((dividend - modulo) / 26);
+      }
+
+      return columnName;
+    }
+
+    private readonly Dictionary<string, string> variableNameMapping = new Dictionary<string, string>();
+    private int currentVariableIndex = 0;
+    private string GetColumnToVariableName(string variabelName) {
+      if (!variableNameMapping.ContainsKey(variabelName)) {
+        currentVariableIndex++;
+        variableNameMapping.Add(variabelName, GetExcelColumnName(currentVariableIndex));
+      }
+      return string.Format("${0}1", variableNameMapping[variabelName]);
+    }
+    public string Format(ISymbolicExpressionTree symbolicExpressionTree) {
+      return Format(symbolicExpressionTree, null);
+    }
+
+    public string Format(ISymbolicExpressionTree symbolicExpressionTree, Dataset dataset) {
+      var stringBuilder = new StringBuilder();
+      if (dataset != null) CalculateVariableMapping(symbolicExpressionTree, dataset);
+
+      stringBuilder.Append("=");
+      stringBuilder.Append(FormatRecursively(symbolicExpressionTree.Root));
+
+      foreach (var variable in variableNameMapping) {
+        stringBuilder.AppendLine();
+        stringBuilder.Append(variable.Key + " = " + variable.Value);
+      }
+      return stringBuilder.ToString();
+    }
+
+    private void CalculateVariableMapping(ISymbolicExpressionTree tree, Dataset dataset) {
+      int columnIndex = 0;
+      int inputIndex = 0;
+      var usedVariables = tree.IterateNodesPrefix().OfType<VariableTreeNode>().Select(v => v.VariableName).Distinct();
+      foreach (var variable in dataset.VariableNames) {
+        columnIndex++;
+        if (!usedVariables.Contains(variable)) continue;
+        inputIndex++;
+        variableNameMapping[variable] = GetExcelColumnName(inputIndex);
+      }
+    }
+
+    private string FormatRecursively(ISymbolicExpressionTreeNode node) {
+      ISymbol symbol = node.Symbol;
+      StringBuilder stringBuilder = new StringBuilder();
+
+      if (symbol is ProgramRootSymbol) {
+        stringBuilder.AppendLine(FormatRecursively(node.GetSubtree(0)));
+      } else if (symbol is StartSymbol)
+        return FormatRecursively(node.GetSubtree(0));
+      else if (symbol is Addition) {
+        stringBuilder.Append("(");
+        for (int i = 0; i < node.SubtreeCount; i++) {
+          if (i > 0) stringBuilder.Append("+");
+          stringBuilder.Append(FormatRecursively(node.GetSubtree(i)));
+        }
+        stringBuilder.Append(")");
+      } else if (symbol is Average) {
+        stringBuilder.Append("(1/");
+        stringBuilder.Append(node.SubtreeCount);
+        stringBuilder.Append(")*(");
+        for (int i = 0; i < node.SubtreeCount; i++) {
+          if (i > 0) stringBuilder.Append("+");
+          stringBuilder.Append("(");
+          stringBuilder.Append(FormatRecursively(node.GetSubtree(i)));
+          stringBuilder.Append(")");
+        }
+        stringBuilder.Append(")");
+      } else if (symbol is Constant) {
+        ConstantTreeNode constantTreeNode = node as ConstantTreeNode;
+        stringBuilder.Append(constantTreeNode.Value.ToString(CultureInfo.InvariantCulture));
+      } else if (symbol is Cosine) {
+        stringBuilder.Append("COS(");
+        stringBuilder.Append(FormatRecursively(node.GetSubtree(0)));
+        stringBuilder.Append(")");
+      } else if (symbol is Division) {
+        if (node.SubtreeCount == 1) {
+          stringBuilder.Append("1/");
+          stringBuilder.Append(FormatRecursively(node.GetSubtree(0)));
+        } else {
+          stringBuilder.Append(FormatRecursively(node.GetSubtree(0)));
+          stringBuilder.Append("/(");
+          for (int i = 1; i < node.SubtreeCount; i++) {
+            if (i > 1) stringBuilder.Append("*");
+            stringBuilder.Append(FormatRecursively(node.GetSubtree(i)));
+          }
+          stringBuilder.Append(")");
+        }
+      } else if (symbol is Exponential) {
+        stringBuilder.Append("EXP(");
+        stringBuilder.Append(FormatRecursively(node.GetSubtree(0)));
+        stringBuilder.Append(")");
+      } else if (symbol is Square) {
+        stringBuilder.Append("POWER(");
+        stringBuilder.Append(FormatRecursively(node.GetSubtree(0)));
+        stringBuilder.Append(",2)");
+      } else if (symbol is SquareRoot) {
+        stringBuilder.Append("SQRT(");
+        stringBuilder.Append(FormatRecursively(node.GetSubtree(0)));
+        stringBuilder.Append(")");
+      } else if (symbol is Logarithm) {
+        stringBuilder.Append("LN(");
+        stringBuilder.Append(FormatRecursively(node.GetSubtree(0)));
+        stringBuilder.Append(")");
+      } else if (symbol is Multiplication) {
+        for (int i = 0; i < node.SubtreeCount; i++) {
+          if (i > 0) stringBuilder.Append("*");
+          stringBuilder.Append(FormatRecursively(node.GetSubtree(i)));
+        }
+      } else if (symbol is Sine) {
+        stringBuilder.Append("SIN(");
+        stringBuilder.Append(FormatRecursively(node.GetSubtree(0)));
+        stringBuilder.Append(")");
+      } else if (symbol is Subtraction) {
+        stringBuilder.Append("(");
+        if (node.SubtreeCount == 1) {
+          stringBuilder.Append("-");
+          stringBuilder.Append(FormatRecursively(node.GetSubtree(0)));
+        } else {
+          stringBuilder.Append(FormatRecursively(node.GetSubtree(0)));
+          for (int i = 1; i < node.SubtreeCount; i++) {
+            stringBuilder.Append("-");
+            stringBuilder.Append(FormatRecursively(node.GetSubtree(i)));
+          }
+        }
+        stringBuilder.Append(")");
+      } else if (symbol is Tangent) {
+        stringBuilder.Append("TAN(");
+        stringBuilder.Append(FormatRecursively(node.GetSubtree(0)));
+        stringBuilder.Append(")");
+
+      } else if (symbol is Variable) {
+        VariableTreeNode variableTreeNode = node as VariableTreeNode;
+        stringBuilder.Append(variableTreeNode.Weight.ToString(CultureInfo.InvariantCulture));
+        stringBuilder.Append("*");
+        stringBuilder.Append(GetColumnToVariableName(variableTreeNode.VariableName));// + LagToString(currentLag));
+      } else if (symbol is Power) {
+        stringBuilder.Append("POWER(");
+        stringBuilder.Append(FormatRecursively(node.GetSubtree(0)));
+        stringBuilder.Append(",ROUND(");
+        stringBuilder.Append(FormatRecursively(node.GetSubtree(1)));
+        stringBuilder.Append(",0))");
+      } else if (symbol is Root) {
+        stringBuilder.Append("(");
+        stringBuilder.Append(FormatRecursively(node.GetSubtree(0)));
+        stringBuilder.Append(")^(1 / ROUND(");
+        stringBuilder.Append(FormatRecursively(node.GetSubtree(1)));
+        stringBuilder.Append(",0))");
+      } else {
+        throw new NotImplementedException("Excel export of " + node.Symbol + " is not implemented.");
+      }
+      return stringBuilder.ToString();
+    }
+  }
+}
Index: stable/HeuristicLab.Problems.DataAnalysis.Symbolic/3.4/HeuristicLab.Problems.DataAnalysis.Symbolic-3.4.csproj
===================================================================
--- stable/HeuristicLab.Problems.DataAnalysis.Symbolic/3.4/HeuristicLab.Problems.DataAnalysis.Symbolic-3.4.csproj	(revision 9862)
+++ stable/HeuristicLab.Problems.DataAnalysis.Symbolic/3.4/HeuristicLab.Problems.DataAnalysis.Symbolic-3.4.csproj	(revision 9931)
@@ -139,5 +139,6 @@
     <Compile Include="Crossovers\SymbolicDataAnalysisExpressionProbabilisticFunctionalCrossover.cs" />
     <Compile Include="Crossovers\SymbolicDataAnalysisExpressionSemanticSimilarityCrossover.cs" />
-    <Compile Include="Formatters\SymbolicDataAnalysisExpressionSmalltalkFormatter.cs" />
+    <Compile Include="Formatters\SymbolicDataAnalysisExpressionExcelFormatter.cs" />
+	<Compile Include="Formatters\SymbolicDataAnalysisExpressionSmalltalkFormatter.cs" />
     <Compile Include="Interfaces\ISymbolicDataAnalysisExpressionCrossover.cs" />
     <Compile Include="Interfaces\ISymbolicDataAnalysisImpactValuesCalculator.cs" />
Index: stable/HeuristicLab.Problems.DataAnalysis.Symbolic/3.4/Interfaces/ISymbolicDataAnalysisModel.cs
===================================================================
--- stable/HeuristicLab.Problems.DataAnalysis.Symbolic/3.4/Interfaces/ISymbolicDataAnalysisModel.cs	(revision 9862)
+++ stable/HeuristicLab.Problems.DataAnalysis.Symbolic/3.4/Interfaces/ISymbolicDataAnalysisModel.cs	(revision 9931)
@@ -25,4 +25,7 @@
     ISymbolicExpressionTree SymbolicExpressionTree { get; }
     ISymbolicDataAnalysisExpressionTreeInterpreter Interpreter { get; }
+
+    double LowerEstimationLimit { get; }
+    double UpperEstimationLimit { get; }
   }
 }
Index: stable/HeuristicLab.Problems.DataAnalysis.Symbolic/3.4/SymbolicDataAnalysisModel.cs
===================================================================
--- stable/HeuristicLab.Problems.DataAnalysis.Symbolic/3.4/SymbolicDataAnalysisModel.cs	(revision 9862)
+++ stable/HeuristicLab.Problems.DataAnalysis.Symbolic/3.4/SymbolicDataAnalysisModel.cs	(revision 9931)
@@ -38,4 +38,10 @@
 
     #region properties
+    [Storable]
+    private double lowerEstimationLimit;
+    public double LowerEstimationLimit { get { return lowerEstimationLimit; } }
+    [Storable]
+    private double upperEstimationLimit;
+    public double UpperEstimationLimit { get { return upperEstimationLimit; } }
 
     [Storable]
@@ -50,5 +56,4 @@
       get { return interpreter; }
     }
-
     #endregion
 
@@ -59,6 +64,9 @@
       this.symbolicExpressionTree = cloner.Clone(original.symbolicExpressionTree);
       this.interpreter = cloner.Clone(original.interpreter);
+      this.lowerEstimationLimit = original.lowerEstimationLimit;
+      this.upperEstimationLimit = original.upperEstimationLimit;
     }
-    public SymbolicDataAnalysisModel(ISymbolicExpressionTree tree, ISymbolicDataAnalysisExpressionTreeInterpreter interpreter)
+    protected SymbolicDataAnalysisModel(ISymbolicExpressionTree tree, ISymbolicDataAnalysisExpressionTreeInterpreter interpreter,
+       double lowerEstimationLimit, double upperEstimationLimit)
       : base() {
       this.name = ItemName;
@@ -66,4 +74,6 @@
       this.symbolicExpressionTree = tree;
       this.interpreter = interpreter;
+      this.lowerEstimationLimit = lowerEstimationLimit;
+      this.upperEstimationLimit = upperEstimationLimit;
     }
 
