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source: stable/HeuristicLab.Problems.DataAnalysis/3.4/DatasetExtensions.cs

Last change on this file was 17181, checked in by swagner, 3 years ago

#2875: Merged r17180 from trunk to stable

File size: 4.8 KB
Line 
1#region License Information
2/* HeuristicLab
3 * Copyright (C) Heuristic and Evolutionary Algorithms Laboratory (HEAL)
4 *
5 * This file is part of HeuristicLab.
6 *
7 * HeuristicLab is free software: you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License as published by
9 * the Free Software Foundation, either version 3 of the License, or
10 * (at your option) any later version.
11 *
12 * HeuristicLab is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15 * GNU General Public License for more details.
16 *
17 * You should have received a copy of the GNU General Public License
18 * along with HeuristicLab. If not, see <http://www.gnu.org/licenses/>.
19 */
20#endregion
21
22using System;
23using System.Collections.Generic;
24using System.Linq;
25
26namespace HeuristicLab.Problems.DataAnalysis {
27  public static class DatasetExtensions {
28    public static double[,] ToArray(this IDataset dataset, IEnumerable<string> variables, IEnumerable<int> rows) {
29      return ToArray(dataset,
30        variables,
31        transformations: variables.Select(_ => (ITransformation<double>)null), // no transform
32        rows: rows);
33    }
34    public static double[,] ToArray(this IDataset dataset, IEnumerable<string> variables,
35      IEnumerable<ITransformation<double>> transformations, IEnumerable<int> rows) {
36      string[] variablesArr = variables.ToArray();
37      int[] rowsArr = rows.ToArray();
38      ITransformation<double>[] transformArr = transformations.ToArray();
39      if (transformArr.Length != variablesArr.Length)
40        throw new ArgumentException("Number of variables and number of transformations must match.");
41
42      double[,] matrix = new double[rowsArr.Length, variablesArr.Length];
43
44      for (int i = 0; i < variablesArr.Length; i++) {
45        var origValues = dataset.GetDoubleValues(variablesArr[i], rowsArr);
46        var values = transformArr[i] != null ? transformArr[i].Apply(origValues) : origValues;
47        int row = 0;
48        foreach (var value in values) {
49          matrix[row, i] = value;
50          row++;
51        }
52      }
53
54      return matrix;
55    }
56
57    /// <summary>
58    /// Prepares a binary data matrix from a number of factors and specified factor values
59    /// </summary>
60    /// <param name="dataset">A dataset that contains the variable values</param>
61    /// <param name="factorVariables">An enumerable of categorical variables (factors). For each variable an enumerable of values must be specified.</param>
62    /// <param name="rows">An enumerable of row indices for the dataset</param>
63    /// <returns></returns>
64    /// <remarks>Factor variables (categorical variables) are split up into multiple binary variables one for each specified value.</remarks>
65    public static double[,] ToArray(
66      this IDataset dataset,
67      IEnumerable<KeyValuePair<string, IEnumerable<string>>> factorVariables,
68      IEnumerable<int> rows) {
69      // check input variables. Only string variables are allowed.
70      var invalidInputs =
71        factorVariables.Select(kvp => kvp.Key).Where(name => !dataset.VariableHasType<string>(name));
72      if (invalidInputs.Any())
73        throw new NotSupportedException("Unsupported inputs: " + string.Join(", ", invalidInputs));
74
75      int numBinaryColumns = factorVariables.Sum(kvp => kvp.Value.Count());
76
77      List<int> rowsList = rows.ToList();
78      double[,] matrix = new double[rowsList.Count, numBinaryColumns];
79
80      int col = 0;
81      foreach (var kvp in factorVariables) {
82        var varName = kvp.Key;
83        var cats = kvp.Value;
84        if (!cats.Any()) continue;
85        foreach (var cat in cats) {
86          var values = dataset.GetStringValues(varName, rows);
87          int row = 0;
88          foreach (var value in values) {
89            matrix[row, col] = value == cat ? 1 : 0;
90            row++;
91          }
92          col++;
93        }
94      }
95      return matrix;
96    }
97
98    public static IEnumerable<KeyValuePair<string, IEnumerable<string>>> GetFactorVariableValues(
99      this IDataset ds, IEnumerable<string> factorVariables, IEnumerable<int> rows) {
100      return from factor in factorVariables
101             let distinctValues = ds.GetStringValues(factor, rows).Distinct().ToArray()
102             // 1 distinct value => skip (constant)
103             // 2 distinct values => only take one of the two values
104             // >=3 distinct values => create a binary value for each value
105             let reducedValues = distinctValues.Length <= 2
106               ? distinctValues.Take(distinctValues.Length - 1)
107               : distinctValues
108             select new KeyValuePair<string, IEnumerable<string>>(factor, reducedValues);
109    }
110  }
111}
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