matrix multiplication

1>>> a = np.array([[ 5, 1 ,3], 
2                  [ 1, 1 ,1], 
3                  [ 1, 2 ,1]])
4>>> b = np.array([1, 2, 3])
5>>> print a.dot(b)
6array([16, 6, 8])

1import java.util.Arrays;
2import java.util.Scanner;
3public class Matrix {
4
5    private static int counter =0;
6    private static Scanner scanner = new Scanner(System.in);
7    private int rawForArr1 , columnforarr1Andrawsforarr2, columnForArr2 =0; //
8
9    public Matrix(){
10    }
11
12
13    public Matrix(int rawForArr1, int columnforarr1Andrawsforarr2, int columnForArr2) {
14        this.rawForArr1 = rawForArr1;
15        this.columnforarr1Andrawsforarr2 = columnforarr1Andrawsforarr2;
16        this.columnForArr2 = columnForArr2;
17    }
18
19    public void setRawsAndColumn(){
20        setRawsAndColumns();
21    }
22
23    private void setRawsAndColumns(){
24        System.out.println("Enter numbers of raws for the (LEFT ARRAY)");
25        int r1=scanner.nextInt();
26        this.rawForArr1 =r1;
27        System.out.println("\nEnter numbers of columns for the (LEFT ARRAY).\nThis value automatically will be assigned for the raws in the right matrix ensuring 'Valid Multiplication'\n");
28        int colArr1RawArr2 = scanner.nextInt();
29        this.columnforarr1Andrawsforarr2 =colArr1RawArr2;
30        System.out.println("Enter numbers of columns for the (RIGHT ARRAY)");
31        int c2=scanner.nextInt();
32        this.columnForArr2 = c2;
33        double [][] firstArr = new double[r1][colArr1RawArr2];
34        double [][] secondArr = new double[colArr1RawArr2][c2];
35        enterElements(firstArr);
36        enterElements(secondArr);
37        double[][] multiplied =multiplieMatrix(firstArr,secondArr);
38        printValue(multiplied);
39    }
40
41
42    // Print the Matrix as a string of Array
43    public static void printValue(double[][] arr)
44    {
45                System.out.println(Arrays.deepToString(arr));
46    }
47
48    public static double [][] multiplieMatrix(double [][] leftArr,double[][] rightArr){
49        int m = leftArr.length;
50        int n = rightArr[0].length;
51        double [][] sumOfMultiplie = new double[m][n];
52        int lARawIndex =0,rACIndex=0,iterateOnLArrColAndRArrRaw=0;
53        double sum = 0 ;
54        for(lARawIndex =0 ; lARawIndex < leftArr.length ; ++lARawIndex)
55        {
56            for(rACIndex = 0 ; rACIndex < rightArr[0].length ; ++rACIndex)
57            {
58                for(iterateOnLArrColAndRArrRaw = 0 ; iterateOnLArrColAndRArrRaw < rightArr.length ; ++iterateOnLArrColAndRArrRaw)
59                {
60                    sum+= (leftArr[lARawIndex][iterateOnLArrColAndRArrRaw]) * (rightArr[iterateOnLArrColAndRArrRaw][rACIndex]);
61                }
62                sumOfMultiplie[lARawIndex][rACIndex]=sum ;
63                sum=0;
64            }
65        }
66        return sumOfMultiplie ;
67    }
68    /* enter elements of the array*/
69    public static double[][] enterElements(double[][] arr)
70    {
71        counter++;
72        if(counter%2==0){
73            System.out.println("\t***(Enter the elements for the RIGHT array)***\n");
74        }
75        System.out.println("\t ***(Enter the elements for the LEFT array)***\n");
76        for(int i = 0 ; i < arr.length ; ++i) // numbers of raws
77        {
78            for(int j = 0 ; j<arr[0].length ; ++j) // numbers of columns
79            {
80                System.out.println("Enter element in raw #"+(i+1)+" column #"+(j+1));
81                arr[i][j] = scanner.nextDouble();
82            }
83        }
84        return arr ;
85
86    }
87
88//
89//    public static  double[][] recursiveMultiplicationMatrix(double [][] multilplies ){
90//        double[][] nextMatrix =initilizeMatrix();
91//        enterElements(nextMatrix);
92//        int m = nextMatrix.length;
93//        int n = multilplies[0].length;
94//        double [][] sumOfMultiplie = new double[m][n];
95//        int lARawIndex =0,rACIndex=0,iterateOnLArrColAndRArrRaw=0;
96//        int sum = 0 ;
97//        for(lARawIndex =0 ; lARawIndex < nextMatrix.length ; ++lARawIndex)
98//        {
99//            for(rACIndex = 0 ; rACIndex < multilplies[0].length ; ++rACIndex)
100//            {
101//                for(iterateOnLArrColAndRArrRaw = 0 ; iterateOnLArrColAndRArrRaw < multilplies.length ; ++iterateOnLArrColAndRArrRaw)
102//                {
103//                    sum+= (nextMatrix[lARawIndex][iterateOnLArrColAndRArrRaw]) * (multilplies[iterateOnLArrColAndRArrRaw][rACIndex]);
104//                }
105//                sumOfMultiplie[lARawIndex][rACIndex]=sum ;
106//                sum=0;
107//            }
108//        }
109//
110//            String answer = answer();
111//            if (answer.equals("yes")) {
112//                return recursiveMultiplicationMatrix(sumOfMultiplie);
113//
114//            }
115//        return sumOfMultiplie ;
116//
117//    }
118//
119//    public static String answer(){
120//        System.out.println("Do you want to continue to multiple? "+'\n'+"enter yes to continue or any other key to print the 2d matrix");
121//        String answer ;
122//        answer = scanner.nextLine();
123//        return answer;
124//    }
125
126
127
128}