Java Variance variance(double[] vector)

Description

variance

License

Apache License

Declaration

public static double variance(double[] vector) 

Method Source Code

//package com.java2s;
/*//from ww w  . j  a v a2 s.  c o  m
 *
 *  * Copyright 2015 Skymind,Inc.
 *  *
 *  *    Licensed 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.
 *
 */

public class Main {
    public static double variance(double[] vector) {
        return sumOfMeanDifferencesOnePoint(vector) / vector.length;
    }

    /**
     * Used for calculating top part of simple regression for
     * beta 1
     * @param vector the x coordinates
     * @return the sum of mean differences for the input vectors
     */
    public static double sumOfMeanDifferencesOnePoint(double[] vector) {
        double mean = sum(vector) / vector.length;
        double ret = 0;
        for (int i = 0; i < vector.length; i++) {
            double vec1Diff = Math.pow(vector[i] - mean, 2);
            ret += vec1Diff;
        }
        return ret;
    }

    /**
     * This returns the sum of the given array.
     * @param nums the array of numbers to sum
     * @return the sum of the given array
     */
    public static double sum(double[] nums) {

        double ret = 0;
        for (double d : nums)
            ret += d;

        return ret;
    }
}

Related

1. variance(double[] population)
2. variance(double[] v)
3. variance(double[] vals)
4. variance(double[] values)
5. variance(double[] values, boolean isUnbiased)
6. variance(double[] vector)
7. variance(double[] vector)
8. variance(final double[] values)
9. variance(final double[] values, final double mean)