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

All Methods Instance Methods Concrete Methods
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
clone, equals, finalize, 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()
```

Class Array2D

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

Array2D

Array2D

Array2D

Array2D

Method Detail

nrows

ncols

apply

get

set

add

sub

mul

div

add

sub

mul

div

add

sub

mul

div

replaceNaN

sum