1 files changed, 99 insertions, 0 deletions
diff --git a/src/de/lmu/ifi/dbs/elki/utilities/scaling/outlier/MultiplicativeInverseScaling.java b/src/de/lmu/ifi/dbs/elki/utilities/scaling/outlier/MultiplicativeInverseScaling.java
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+++ b/src/de/lmu/ifi/dbs/elki/utilities/scaling/outlier/MultiplicativeInverseScaling.java
@@ -0,0 +1,99 @@
+package de.lmu.ifi.dbs.elki.utilities.scaling.outlier;
+/*
+This file is part of ELKI:
+Environment for Developing KDD-Applications Supported by Index-Structures
+
+Copyright (C) 2011
+Ludwig-Maximilians-Universität München
+Lehr- und Forschungseinheit für Datenbanksysteme
+ELKI Development Team
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU Affero General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program 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 Affero General Public License for more details.
+
+You should have received a copy of the GNU Affero General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+import de.lmu.ifi.dbs.elki.database.ids.DBID;
+import de.lmu.ifi.dbs.elki.result.outlier.OutlierResult;
+import de.lmu.ifi.dbs.elki.utilities.documentation.Reference;
+
+/**
+ * Scaling function to invert values basically by computing 1/x, but in a variation
+ * that maps the values to the [0:1] interval and avoiding division by 0.
+ * 
+ * The exact formula can be written as
+ * 
+ * 1 / (value * max_{x!=0}(1 / abs(x))) = min_{x != 0}(abs(x)) / x
+ * 
+ * with 1 / 0 := 1
+ * 
+ * @author Erich Schubert
+ */
+@Reference(authors="H.-P. Kriegel, P. Kröger, E. Schubert, A. Zimek", title="Interpreting and Unifying Outlier Scores", booktitle="Proc. 11th SIAM International Conference on Data Mining (SDM), Mesa, AZ, 2011", url="http://www.dbs.ifi.lmu.de/~zimek/publications/SDM2011/SDM11-outlier-preprint.pdf")
+public class MultiplicativeInverseScaling implements OutlierScalingFunction {
+  /**
+   * Constructor, adhering to
+   * {@link de.lmu.ifi.dbs.elki.utilities.optionhandling.Parameterizable}
+   */
+  public MultiplicativeInverseScaling() {
+    super();
+  }
+
+  /**
+   * Scaling value, set by {@link #prepare}.
+   */
+  double scaleval = 0;
+
+  @Override
+  public double getScaled(double value) {
+    assert (scaleval != 0) : "prepare() was not run prior to using the scaling function.";
+    try {
+      return 1.0 / (value * scaleval);
+    }
+    catch(ArithmeticException e) {
+      return 1.0;
+    }
+  }
+
+  @Override
+  public void prepare(OutlierResult or) {
+    scaleval = getScaleValue(or);
+  }
+
+  /**
+   * Compute the scaling value in a linear scan over the annotation.
+   * 
+   * @param or Outlier result
+   * @return Scaling value.
+   */
+  private static double getScaleValue(OutlierResult or) {
+    double max = Double.MIN_VALUE;
+    for(DBID id : or.getScores().iterDBIDs()) {
+      double val = or.getScores().get(id);
+      double inv = Math.abs(1.0 / val);
+      if(!Double.isInfinite(inv) && !Double.isNaN(inv)) {
+        max = Math.max(max, inv);
+      }
+    }
+    return max;
+  }
+  
+  @Override
+  public double getMin() {
+    return 0.0;
+  }
+  
+  @Override
+  public double getMax() {
+    return 1.0;
+  }
+}
+\ No newline at end of file