import java.util.Arrays; public class Matrix { public static void main(String[] args) { double[][] a = {{1,2,3},{0,1, -1}}; double[][] b = {{1},{0}}; double[][] t = {{1,2,3,4},{5,6,7,8}}; System.out.println("original:"); for(double[] x : t) System.out.println(Arrays.toString(x)); System.out.println("\ntransposed: "); for(double[] x : (t= transpose(t))) System.out.println(Arrays.toString(x)); System.out.println("\nmultiplied with 5:"); for(double[] x : (t = scalarMul(5.0, t))) System.out.println(Arrays.toString(x)); System.out.println("\na="); for(double[] x : a) System.out.println(Arrays.toString(x)); System.out.println("\nmultiplied with a:"); for(double[] x : (t = mul(t, a))) System.out.println(Arrays.toString(x)); } public static double[][] sub(double[][] a, double[][] b){ int rows = a.length; int columns = a[0].length; double[][] c = new double[rows][columns]; for(int i = 0; i < rows; i++){ for(int j = 0; j < columns; j++){ c[i][j] = a[i][j] - b[i][j]; } } return c; } public static double[][] add(double[][] a, double[][] b){ int rows = a.length; int columns = a[0].length; double[][] c = new double[rows][columns]; for(int i = 0; i < rows; i++){ for(int j = 0; j < columns; j++){ c[i][j] = a[i][j] + b[i][j]; } } return c; } public static double[][] mul(double[][] a, double[][] b){ int rows = a.length; int columns = b[0].length; double[][] c = new double[rows][columns]; for(int i = 0; i < columns; i++){ for(int j = 0; j < rows; j++){ for (int k = 0; k < b.length; k++){ c[j][i] += a[j][k]*b[k][i]; } } } return c; } public static double[][] scalarMul(double a, double[][] b){ int rows = b.length; int columns = b[0].length; double[][] c = new double[rows][columns]; for(int i = 0; i < rows; i ++){ for(int j = 0; j < columns; j++){ c[i][j] = a * b[i][j]; } } return c; } public static double[][] transpose(double[][] a){ int rows = a.length; int columns = a[0].length; double[][] t = new double[columns][rows]; for(int i = 0; i < rows; i++){ for(int j = 0; j < columns; j++){ t[j][i] = a[i][j]; } } return t; } }

stuff with matrices