Package com.katiejergens.matrixmath

Class Matrix

java.lang.Object

com.katiejergens.matrixmath.Matrix

public class Matrix
extends java.lang.Object

Field Summary

Fields

Modifier and Type	Field	Description
double[][]	matrix	Holds the values of the matrix

Constructor Summary

Constructors

Constructor	Description
Matrix()	Default constructor
Matrix(double[][] matrix)	Create a Matrix object from a 2D array.
Matrix(int rows, int columns)	Create a Matrix object with the given number of rows and columns.
Matrix(int rows, int columns, double value)	Create a Matrix object with the given number of rows and columns and set all spots to the given value.

Method Summary

Modifier and Type	Method	Description
Matrix	augment()	Return an augmented matrix, which is the matrix concatenated to the identity matrix.
int	getColumnCount()	Get how many columns.
double[][]	getMatrix()	Get the matrix array.
int	getRowCount()	Get how many rows.
double	getValueAt(int row, int column)	Get the specific value at the given row and column.
Matrix	invert()	Inverts a matrix.
Matrix	linearCombRows(double scalar, int sourceRow, int destRow)	Adds a scalar multiple of the first row to the second row.
Matrix	plus(Matrix matrix)	Add matrices and return the sum.
Matrix	rowReduce()	Row reduces a matrix.
double[]	scalarTimesRow(double scalar, int row)	Multiplies a scalar times a row.
void	setEntry(int row, int column, double value)	Set a specific value at the given row and column.
Matrix	switchRows(int firstrow, int secondrow)	Switch two rows of a matrix.
Matrix	times(Matrix matrix)	Multiply this matrix to the given matrix and return the product.
java.lang.String	toString()	Composes a string representation of the matrix

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

matrix

private double[][] matrix

Holds the values of the matrix

Constructor Detail

Matrix

public Matrix()

Default constructor

Matrix

public Matrix(double[][] matrix)

Create a Matrix object from a 2D array.

Parameters:

matrix - a 2D array of doubles

Matrix

public Matrix(int rows,
              int columns)

Create a Matrix object with the given number of rows and columns. It will automatically initialize with all zeros.

Parameters:

rows - number of rows

columns - number of columns

Matrix

public Matrix(int rows,
              int columns,
              double value)

Create a Matrix object with the given number of rows and columns and set all spots to the given value.

Parameters:

rows -

columns -

value -

Method Detail

getMatrix

public double[][] getMatrix()

Get the matrix array.

Returns:

a 2D double array

getRowCount

public int getRowCount()

Get how many rows.

Returns:

int

getColumnCount

public int getColumnCount()

Get how many columns.

Returns:

int

getValueAt

public double getValueAt(int row,
                         int column)

Get the specific value at the given row and column.

Parameters:

row -

column -

Returns:

double

setEntry

public void setEntry(int row,
                     int column,
                     double value)

Set a specific value at the given row and column.

Parameters:

row -

column -

value -

plus

public Matrix plus(Matrix matrix)

Add matrices and return the sum. Does not change this matrix.

Parameters:

matrix - Matrix to add

Returns:

The sum of this matrix and the given matrix.

scalarTimesRow

public double[] scalarTimesRow(double scalar,
                               int row)

Multiplies a scalar times a row. For example, trixie.scalarTimesRow(2.0,3) multiplies row three of trixie by two.

Parameters:

scalar - The value to multiply by

row - Row number to change

Returns:

An array/row of the products.

times

public Matrix times(Matrix matrix)

Multiply this matrix to the given matrix and return the product. (Does not change this matrix.)

Parameters:

matrix -

Returns:

a Matrix

switchRows

public Matrix switchRows(int firstrow,
                         int secondrow)

Switch two rows of a matrix. For example, trixie.switchRows(3,5) exchanges rows three and five of the matrix trixie.

Parameters:

firstrow -

secondrow -

Returns:

The switched matrix.

linearCombRows

public Matrix linearCombRows(double scalar,
                             int sourceRow,
                             int destRow)

Adds a scalar multiple of the first row to the second row. For example, trixie.linearCombRows(.5,3,2) adds .5 times row three to row two.

Parameters:

scalar -

sourceRow -

destRow -

Returns:

The new matrix.

rowReduce

public Matrix rowReduce()

Row reduces a matrix. For example, trixie.rowreduce() should return the row reduction of trixie. rowreduce should work for all matrices.

Returns:

The reduced matrix

augment

public Matrix augment()

Return an augmented matrix, which is the matrix concatenated to the identity matrix. E.g. 1 0 1 0 0 1 2 1 0 0 1 2 0 0 0 1 The augmented form is: 1 0 1 0 1 0 0 0 0 1 2 1 0 1 0 0 0 0 1 2 0 0 1 0 0 0 0 1 0 0 0 1

Returns:

invert

public Matrix invert()

Inverts a matrix. For example, trixie.invert() should return the inverse matrix of trixie. invert should work for square matrices which are invertible.

Returns:

The inverted matrix

toString

public java.lang.String toString()

Composes a string representation of the matrix

Overrides:

toString in class java.lang.Object

Returns:

A string of the rows x columms.