smile.math

Class Array2D

java.lang.Object

smile.math.Array2D

public class Array2D
extends java.lang.Object

2-dimensional array of doubles. Java doesn't have real multidimensional arrays. They are just array of arrays, which are not friendly to modern CPU due to frequent cache miss. The extra (multiple times) array index checking also significantly reduces the performance. This class solves these pain points by storing data in a single 1D array of doubles in row major order. Note that this class is simple by design, as a replacement of double[][] in case of row by row access. For advanced matrix computation, please use Matrix.

See Also:

Matrix

Constructor Summary

Constructors

Constructor and Description
Array2D(double[][] A) Constructor.
Array2D(int rows, int cols) Constructor of all-zero matrix.
Array2D(int rows, int cols, double value) Constructor.
Array2D(int rows, int cols, double[] value) Constructor.

Method Summary

Modifier and Type	Method and Description
Array2D	add(Array2D b)
Array2D	add(double x)
double	add(int i, int j, double x)
double	apply(int i, int j) Returns A(i, j).
Array2D	div(Array2D b)
Array2D	div(double x)
double	div(int i, int j, double x)
double	get(int i, int j) Returns A(i, j).
Array2D	mul(Array2D b)
Array2D	mul(double x)
double	mul(int i, int j, double x)
int	ncols()
int	nrows()
Array2D	replaceNaN(double x)
double	set(int i, int j, double x) Sets A(i, j).
Array2D	sub(Array2D b)
Array2D	sub(double x)
double	sub(int i, int j, double x)
double	sum()

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Array2D

public Array2D(double[][] A)

Constructor.

Parameters:

A - the array of matrix.

Array2D

public Array2D(int rows,
               int cols)

Constructor of all-zero matrix.

Array2D

public Array2D(int rows,
               int cols,
               double value)

Constructor. Fill the matrix with given value.

Array2D

public Array2D(int rows,
               int cols,
               double[] value)

Constructor.

Parameters:

value - the array of matrix values arranged in row major format

Method Detail

nrows

public int nrows()

ncols

public int ncols()

apply

public double apply(int i,
                    int j)

Returns A(i, j). Useful in Scala.

get

public double get(int i,
                  int j)

Returns A(i, j).

set

public double set(int i,
                  int j,
                  double x)

Sets A(i, j).

add

public double add(int i,
                  int j,
                  double x)

sub

public double sub(int i,
                  int j,
                  double x)

mul

public double mul(int i,
                  int j,
                  double x)

div

public double div(int i,
                  int j,
                  double x)

add

public Array2D add(Array2D b)

sub

public Array2D sub(Array2D b)

mul

public Array2D mul(Array2D b)

div

public Array2D div(Array2D b)

add

public Array2D add(double x)

sub

public Array2D sub(double x)

mul

public Array2D mul(double x)

div

public Array2D div(double x)

replaceNaN

public Array2D replaceNaN(double x)

sum

public double sum()