Merge pull request #245 from eclipse/add_outlier_stats

Add outlier stats class

org.eclipse.dawnsci.analysis.dataset/src/org/eclipse/dawnsci/analysis/dataset/impl/Outliers.java

@@ -0,0 +1,61 @@
+/*-
+ * Copyright 2016 Diamond Light Source Ltd.
+ *
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ */
+
+package org.eclipse.dawnsci.analysis.dataset.impl;
+
+public class Outliers {
+
+	private final static double MADSCALEFACTOR = 1.4826;
+	private final static double SNSCALEFACTOR = 1.1926;
+
+	public static double[] medianAbsoluteDeviation(Dataset data) {
+
+		double median = (Double)Stats.median(data);
+		data = Maths.subtract(data, median);
+		data = Maths.abs(data);
+		double median2 = (Double)Stats.median(data);
+		double mad = MADSCALEFACTOR * median2;
+
+		return new double[]{mad, median};
+	}
+
+	public static double snNaive(Dataset data) {
+
+		Dataset medAbs = DatasetFactory.zeros(data);
+		Dataset dif = DatasetFactory.zeros(data);
+
+		IndexIterator it = data.getIterator();
+		int count = 0;
+		while (it.hasNext()) {
+			double val = data.getElementDoubleAbs(it.index);
+			Maths.subtract(data, val, dif);
+			Maths.abs(dif,dif);
+			//Lower median - Math.floor((n/2)+1) of sorted
+			dif.sort(null);
+			medAbs.setObjectAbs(count++, dif.getElementDoubleAbs((int)Math.floor((dif.getSize()/2)+1)));
+		}
+
+
+		//Higher median - Math.floor((n+1)/2) of sorted
+		medAbs.sort(null);
+		double median = medAbs.getElementDoubleAbs((int)Math.floor((medAbs.getSize()+1)/2));
+
+		return median * SNSCALEFACTOR;
+	}
+
+	public static double lowMed(Dataset data) {
+		return data.getElementDoubleAbs((int)Math.floor((data.getSize()/2)+1));
+	}
+
+	public static double highMed(Dataset data) {
+		return data.getElementDoubleAbs((int)Math.floor((data.getSize()+1)/2));
+	}
+
+
+}