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diff --git a/src/main/java/org/apache/commons/math3/stat/descriptive/moment/VectorialCovariance.java b/src/main/java/org/apache/commons/math3/stat/descriptive/moment/VectorialCovariance.java
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+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.commons.math3.stat.descriptive.moment;
+
+import java.io.Serializable;
+import java.util.Arrays;
+
+import org.apache.commons.math3.exception.DimensionMismatchException;
+import org.apache.commons.math3.linear.MatrixUtils;
+import org.apache.commons.math3.linear.RealMatrix;
+
+/**
+ * Returns the covariance matrix of the available vectors.
+ * @since 1.2
+ */
+public class VectorialCovariance implements Serializable {
+
+ /** Serializable version identifier */
+ private static final long serialVersionUID = 4118372414238930270L;
+
+ /** Sums for each component. */
+ private final double[] sums;
+
+ /** Sums of products for each component. */
+ private final double[] productsSums;
+
+ /** Indicator for bias correction. */
+ private final boolean isBiasCorrected;
+
+ /** Number of vectors in the sample. */
+ private long n;
+
+ /** Constructs a VectorialCovariance.
+ * @param dimension vectors dimension
+ * @param isBiasCorrected if true, computed the unbiased sample covariance,
+ * otherwise computes the biased population covariance
+ */
+ public VectorialCovariance(int dimension, boolean isBiasCorrected) {
+ sums = new double[dimension];
+ productsSums = new double[dimension * (dimension + 1) / 2];
+ n = 0;
+ this.isBiasCorrected = isBiasCorrected;
+ }
+
+ /**
+ * Add a new vector to the sample.
+ * @param v vector to add
+ * @throws DimensionMismatchException if the vector does not have the right dimension
+ */
+ public void increment(double[] v) throws DimensionMismatchException {
+ if (v.length != sums.length) {
+ throw new DimensionMismatchException(v.length, sums.length);
+ }
+ int k = 0;
+ for (int i = 0; i < v.length; ++i) {
+ sums[i] += v[i];
+ for (int j = 0; j <= i; ++j) {
+ productsSums[k++] += v[i] * v[j];
+ }
+ }
+ n++;
+ }
+
+ /**
+ * Get the covariance matrix.
+ * @return covariance matrix
+ */
+ public RealMatrix getResult() {
+
+ int dimension = sums.length;
+ RealMatrix result = MatrixUtils.createRealMatrix(dimension, dimension);
+
+ if (n > 1) {
+ double c = 1.0 / (n * (isBiasCorrected ? (n - 1) : n));
+ int k = 0;
+ for (int i = 0; i < dimension; ++i) {
+ for (int j = 0; j <= i; ++j) {
+ double e = c * (n * productsSums[k++] - sums[i] * sums[j]);
+ result.setEntry(i, j, e);
+ result.setEntry(j, i, e);
+ }
+ }
+ }
+
+ return result;
+
+ }
+
+ /**
+ * Get the number of vectors in the sample.
+ * @return number of vectors in the sample
+ */
+ public long getN() {
+ return n;
+ }
+
+ /**
+ * Clears the internal state of the Statistic
+ */
+ public void clear() {
+ n = 0;
+ Arrays.fill(sums, 0.0);
+ Arrays.fill(productsSums, 0.0);
+ }
+
+ /** {@inheritDoc} */
+ @Override
+ public int hashCode() {
+ final int prime = 31;
+ int result = 1;
+ result = prime * result + (isBiasCorrected ? 1231 : 1237);
+ result = prime * result + (int) (n ^ (n >>> 32));
+ result = prime * result + Arrays.hashCode(productsSums);
+ result = prime * result + Arrays.hashCode(sums);
+ return result;
+ }
+
+ /** {@inheritDoc} */
+ @Override
+ public boolean equals(Object obj) {
+ if (this == obj) {
+ return true;
+ }
+ if (!(obj instanceof VectorialCovariance)) {
+ return false;
+ }
+ VectorialCovariance other = (VectorialCovariance) obj;
+ if (isBiasCorrected != other.isBiasCorrected) {
+ return false;
+ }
+ if (n != other.n) {
+ return false;
+ }
+ if (!Arrays.equals(productsSums, other.productsSums)) {
+ return false;
+ }
+ if (!Arrays.equals(sums, other.sums)) {
+ return false;
+ }
+ return true;
+ }
+
+}