apache commons Math是一組偏向科學計算為主的函式，主要是針對線性代數，數學分析，概率和統計等方面。

     我雖然是數學專業畢業，當年也是抱著《數學分析》啃，但是好久不用，這些概念都開始生疏，寫一點例子，僅作參考。

packagetest.ffm83.commons.math;

importorg.apache.commons.math3.linear.Array2DRowRealMatrix; 

import org.apache.commons.math3.linear.LUDecomposition; 

importorg.apache.commons.math3.linear.RealMatrix; 

importorg.apache.commons.math3.stat.descriptive.moment.GeometricMean; 

importorg.apache.commons.math3.stat.descriptive.moment.Kurtosis; 

importorg.apache.commons.math3.stat.descriptive.moment.Mean; 

importorg.apache.commons.math3.stat.descriptive.moment.Skewness; 

importorg.apache.commons.math3.stat.descriptive.moment.StandardDeviation; 

importorg.apache.commons.math3.stat.descriptive.moment.Variance; 

import org.apache.commons.math3.stat.descriptive.rank.Max; 

importorg.apache.commons.math3.stat.descriptive.rank.Min; 

importorg.apache.commons.math3.stat.descriptive.rank.Percentile; 

importorg.apache.commons.math3.stat.descriptive.summary.Product; 

importorg.apache.commons.math3.stat.descriptive.summary.Sum; 

importorg.apache.commons.math3.stat.descriptive.summary.SumOfSquares;

/**

 * 簡單使用commons Math方法

 * @author 範芳銘

 */

public class MathUsage {

     public static void main(String[] args) { 

        double[] values = new double[] { 0.33, 1.33,0.27333, 0.3, 0.501, 

                0.444, 0.44, 0.34496, 0.33,0.3, 0.292, 0.667 }; 

        Min min = new Min(); 

        Max max = new Max(); 

        Mean mean = new Mean(); // 算術平均值 

        Product product = new Product();//乘積 

        Sum sum = new Sum(); 

        Variance variance = new Variance();//方差 

        System.out.println("min: " +min.evaluate(values)); 

        System.out.println("max: " +max.evaluate(values)); 

        System.out.println("mean: " +mean.evaluate(values)); 

        System.out.println("product:" + product.evaluate(values)); 

        System.out.println("sum: " +sum.evaluate(values)); 

        System.out.println("variance:" + variance.evaluate(values)); 

        Percentile percentile = newPercentile(); // 百分位數 

        GeometricMean geoMean = newGeometricMean(); // 幾何平均數,n個正數的連乘積的n次算術根叫做這n個數的幾何平均數 

        Skewness skewness = new Skewness(); //Skewness(); 

        Kurtosis kurtosis = new Kurtosis(); //Kurtosis,峰度 

        SumOfSquares sumOfSquares = newSumOfSquares(); // 平方和 

        StandardDeviation StandardDeviation =new StandardDeviation();//標準差 

        System.out.println("80 percentilevalue: " 

                + percentile.evaluate(values,80.0)); 

        System.out.println("geometricmean: " + geoMean.evaluate(values)); 

        System.out.println("skewness:" + skewness.evaluate(values)); 

        System.out.println("kurtosis:" + kurtosis.evaluate(values)); 

        System.out.println("sumOfSquares:" + sumOfSquares.evaluate(values)); 

       System.out.println("StandardDeviation: " +StandardDeviation.evaluate(values)); 

       System.out.println("-------------------------------------"); 

        // Create a real matrix with two rowsand three columns 

        double[][] matrixData = { {1d,2d,3d},{2d,5d,3d}}; 

        RealMatrix m = newArray2DRowRealMatrix(matrixData); 

        System.out.println(m); 

        // One more with three rows, twocolumns 

        double[][] matrixData2 = { {1d,2d},{2d,5d}, {1d, 7d}}; 

        RealMatrix n = newArray2DRowRealMatrix(matrixData2);         

        // Note: The constructor copies  the input double[][] array.          

        // Now multiply m by n 

        RealMatrix p = m.multiply(n); 

       System.out.println("p:"+p); 

       System.out.println(p.getRowDimension());    // 2 

       System.out.println(p.getColumnDimension()); // 2          

        // Invert p, using LUdecomposition 

        RealMatrix pInverse = newLUDecomposition(p).getSolver().getInverse(); 

        System.out.println(pInverse); 

    } 

}

執行結果如下：

min: 0.27333

max: 1.33

mean: 0.46269083333333333

product: 2.3429343978460972E-5

sum: 5.552289999999999

variance: 0.08757300031742428

80 percentile value: 0.5674000000000001

geometric mean: 0.4112886050879374

skewness: 2.670095445623868

kurtosis: 7.718241303328169

sumOfSquares: 3.5322966905000004

StandardDeviation: 0.2959273564870681

-------------------------------------

Array2DRowRealMatrix{{1.0,2.0,3.0},{2.0,5.0,3.0}}

p:Array2DRowRealMatrix{{8.0,33.0},{15.0,50.0}}

2

2

Array2DRowRealMatrix{{-0.5263157895,0.3473684211},{0.1578947368,-0.0842105263}}