## weka.classifiers.functions.pace Class Matrix

```java.lang.Object
weka.classifiers.functions.pace.Matrix
```
All Implemented Interfaces:
java.lang.Cloneable, java.io.Serializable
Direct Known Subclasses:
PaceMatrix

public class Matrix
extends java.lang.Object
implements java.lang.Cloneable, java.io.Serializable

Jama = Java Matrix class.

The Java Matrix Class provides the fundamental operations of numerical linear algebra. Various constructors create Matrices from two dimensional arrays of double precision floating point numbers. Various "gets" and "sets" provide access to submatrices and matrix elements. Several methods implement basic matrix arithmetic, including matrix addition and multiplication, matrix norms, and element-by-element array operations. Methods for reading and printing matrices are also included. All the operations in this version of the Matrix Class involve real matrices. Complex matrices may be handled in a future version.

Five fundamental matrix decompositions, which consist of pairs or triples of matrices, permutation vectors, and the like, produce results in five decomposition classes. These decompositions are accessed by the Matrix class to compute solutions of simultaneous linear equations, determinants, inverses and other matrix functions. The five decompositions are:

• Cholesky Decomposition of symmetric, positive definite matrices.
• LU Decomposition of rectangular matrices.
• QR Decomposition of rectangular matrices.
• Singular Value Decomposition of rectangular matrices.
• Eigenvalue Decomposition of both symmetric and nonsymmetric square matrices.
Example of use:

Solve a linear system A x = b and compute the residual norm, ||b - A x||.

```      double[][] vals = {{1.,2.,3},{4.,5.,6.},{7.,8.,10.}};
Matrix A = new Matrix(vals);
Matrix b = Matrix.random(3,1);
Matrix x = A.solve(b);
Matrix r = A.times(x).minus(b);
double rnorm = r.normInf();
```

Version:
5 August 1998
Author:
The MathWorks, Inc. and the National Institute of Standards and Technology.
Serialized Form

 Field Summary `protected  double[][]` `A`           Array for internal storage of elements. `protected  int` `m`           Row and column dimensions. `protected  int` `n`           Row and column dimensions.

 Constructor Summary `Matrix(double[][] A)`           Construct a matrix from a 2-D array. ```Matrix(double[][] A, int m, int n)```           Construct a matrix quickly without checking arguments. ```Matrix(double[] vals, int m)```           Construct a matrix from a one-dimensional packed array ```Matrix(int m, int n)```           Construct an m-by-n matrix of zeros. ```Matrix(int m, int n, double s)```           Construct an m-by-n constant matrix.

 Method Summary ` Matrix` `arrayLeftDivide(Matrix B)`           Element-by-element left division, C = A. ` Matrix` `arrayLeftDivideEquals(Matrix B)`           Element-by-element left division in place, A = A. ` Matrix` `arrayRightDivide(Matrix B)`           Element-by-element right division, C = A. ` Matrix` `arrayRightDivideEquals(Matrix B)`           Element-by-element right division in place, A = A. ` Matrix` `arrayTimes(Matrix B)`           Element-by-element multiplication, C = A. ` Matrix` `arrayTimesEquals(Matrix B)`           Element-by-element multiplication in place, A = A. `private  void` `checkMatrixDimensions(Matrix B)`           Check if size(A) == size(B) ` java.lang.Object` `clone()`           Clone the Matrix object. `static Matrix` `constructWithCopy(double[][] A)`           Construct a matrix from a copy of a 2-D array. ` Matrix` `copy()`           Make a deep copy of a matrix ` double` ```get(int i, int j)```           Get a single element. ` double[][]` `getArray()`           Access the internal two-dimensional array. ` double[][]` `getArrayCopy()`           Copy the internal two-dimensional array. ` int` `getColumnDimension()`           Get column dimension. ` double[]` `getColumnPackedCopy()`           Make a one-dimensional column packed copy of the internal array. ` Matrix` ```getMatrix(int[] r, int[] c)```           Get a submatrix. ` Matrix` ```getMatrix(int[] r, int j0, int j1)```           Get a submatrix. ` Matrix` ```getMatrix(int i0, int i1, int[] c)```           Get a submatrix. ` Matrix` ```getMatrix(int i0, int i1, int j0, int j1)```           Get a submatrix. ` int` `getRowDimension()`           Get row dimension. ` double[]` `getRowPackedCopy()`           Make a one-dimensional row packed copy of the internal array. `static Matrix` ```identity(int m, int n)```           Generate identity matrix ` Matrix` `minus(Matrix B)`           C = A - B ` Matrix` `minusEquals(Matrix B)`           A = A - B ` double` `norm1()`           One norm ` double` `normF()`           Frobenius norm ` double` `normInf()`           Infinity norm ` Matrix` `plus(Matrix B)`           C = A + B ` Matrix` `plusEquals(Matrix B)`           A = A + B ` void` ```print(int w, int d)```           Print the matrix to stdout. ` void` ```print(java.text.NumberFormat format, int width)```           Print the matrix to stdout. ` void` ```print(java.io.PrintWriter output, int w, int d)```           Print the matrix to the output stream. ` void` ```print(java.io.PrintWriter output, java.text.NumberFormat format, int width)```           Print the matrix to the output stream. `static Matrix` ```random(int m, int n)```           Generate matrix with random elements `static Matrix` `read(java.io.BufferedReader input)`           Read a matrix from a stream. ` void` ```set(int i, int j, double s)```           Set a single element. ` void` ```setMatrix(int[] r, int[] c, Matrix X)```           Set a submatrix. ` void` ```setMatrix(int[] r, int j0, int j1, Matrix X)```           Set a submatrix. ` void` ```setMatrix(int i0, int i1, int[] c, Matrix X)```           Set a submatrix. ` void` ```setMatrix(int i0, int i1, int j0, int j1, Matrix X)```           Set a submatrix. ` Matrix` `times(double s)`           Multiply a matrix by a scalar, C = s*A ` Matrix` `times(Matrix B)`           Linear algebraic matrix multiplication, A * B ` Matrix` `timesEquals(double s)`           Multiply a matrix by a scalar in place, A = s*A ` double` `trace()`           Matrix trace. ` Matrix` `transpose()`           Matrix transpose. ` Matrix` `uminus()`           Unary minus

 Methods inherited from class java.lang.Object `equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

 Field Detail

### A

`protected double[][] A`
Array for internal storage of elements.

### m

`protected int m`
Row and column dimensions.

### n

`protected int n`
Row and column dimensions.

 Constructor Detail

### Matrix

```public Matrix(int m,
int n)```
Construct an m-by-n matrix of zeros.

Parameters:
`m` - Number of rows.
`n` - Number of colums.

### Matrix

```public Matrix(int m,
int n,
double s)```
Construct an m-by-n constant matrix.

Parameters:
`m` - Number of rows.
`n` - Number of colums.
`s` - Fill the matrix with this scalar value.

### Matrix

`public Matrix(double[][] A)`
Construct a matrix from a 2-D array.

Parameters:
`A` - Two-dimensional array of doubles.
Throws:
`java.lang.IllegalArgumentException` - All rows must have the same length
`constructWithCopy(double[][])`

### Matrix

```public Matrix(double[][] A,
int m,
int n)```
Construct a matrix quickly without checking arguments.

Parameters:
`A` - Two-dimensional array of doubles.
`m` - Number of rows.
`n` - Number of colums.

### Matrix

```public Matrix(double[] vals,
int m)```
Construct a matrix from a one-dimensional packed array

Parameters:
`vals` - One-dimensional array of doubles, packed by columns (ala Fortran).
`m` - Number of rows.
Throws:
`java.lang.IllegalArgumentException` - Array length must be a multiple of m.
 Method Detail

### constructWithCopy

`public static Matrix constructWithCopy(double[][] A)`
Construct a matrix from a copy of a 2-D array.

Parameters:
`A` - Two-dimensional array of doubles.
Throws:
`java.lang.IllegalArgumentException` - All rows must have the same length

### copy

`public Matrix copy()`
Make a deep copy of a matrix

### clone

`public java.lang.Object clone()`
Clone the Matrix object.

### getArray

`public double[][] getArray()`
Access the internal two-dimensional array.

Returns:
Pointer to the two-dimensional array of matrix elements.

### getArrayCopy

`public double[][] getArrayCopy()`
Copy the internal two-dimensional array.

Returns:
Two-dimensional array copy of matrix elements.

### getColumnPackedCopy

`public double[] getColumnPackedCopy()`
Make a one-dimensional column packed copy of the internal array.

Returns:
Matrix elements packed in a one-dimensional array by columns.

### getRowPackedCopy

`public double[] getRowPackedCopy()`
Make a one-dimensional row packed copy of the internal array.

Returns:
Matrix elements packed in a one-dimensional array by rows.

### getRowDimension

`public int getRowDimension()`
Get row dimension.

Returns:
m, the number of rows.

### getColumnDimension

`public int getColumnDimension()`
Get column dimension.

Returns:
n, the number of columns.

### get

```public double get(int i,
int j)```
Get a single element.

Parameters:
`i` - Row index.
`j` - Column index.
Returns:
A(i,j)
Throws:
`java.lang.ArrayIndexOutOfBoundsException`

### getMatrix

```public Matrix getMatrix(int i0,
int i1,
int j0,
int j1)```
Get a submatrix.

Parameters:
`i0` - Initial row index
`i1` - Final row index
`j0` - Initial column index
`j1` - Final column index
Returns:
A(i0:i1,j0:j1)
Throws:
`java.lang.ArrayIndexOutOfBoundsException` - Submatrix indices

### getMatrix

```public Matrix getMatrix(int[] r,
int[] c)```
Get a submatrix.

Parameters:
`r` - Array of row indices.
`c` - Array of column indices.
Returns:
A(r(:),c(:))
Throws:
`java.lang.ArrayIndexOutOfBoundsException` - Submatrix indices

### getMatrix

```public Matrix getMatrix(int i0,
int i1,
int[] c)```
Get a submatrix.

Parameters:
`i0` - Initial row index
`i1` - Final row index
`c` - Array of column indices.
Returns:
A(i0:i1,c(:))
Throws:
`java.lang.ArrayIndexOutOfBoundsException` - Submatrix indices

### getMatrix

```public Matrix getMatrix(int[] r,
int j0,
int j1)```
Get a submatrix.

Parameters:
`r` - Array of row indices.
Returns:
A(r(:),j0:j1)
Throws:
`java.lang.ArrayIndexOutOfBoundsException` - Submatrix indices

### set

```public void set(int i,
int j,
double s)```
Set a single element.

Parameters:
`i` - Row index.
`j` - Column index.
`s` - A(i,j).
Throws:
`java.lang.ArrayIndexOutOfBoundsException`

### setMatrix

```public void setMatrix(int i0,
int i1,
int j0,
int j1,
Matrix X)```
Set a submatrix.

Parameters:
`i0` - Initial row index
`i1` - Final row index
`j0` - Initial column index
`j1` - Final column index
`X` - A(i0:i1,j0:j1)
Throws:
`java.lang.ArrayIndexOutOfBoundsException` - Submatrix indices

### setMatrix

```public void setMatrix(int[] r,
int[] c,
Matrix X)```
Set a submatrix.

Parameters:
`r` - Array of row indices.
`c` - Array of column indices.
`X` - A(r(:),c(:))
Throws:
`java.lang.ArrayIndexOutOfBoundsException` - Submatrix indices

### setMatrix

```public void setMatrix(int[] r,
int j0,
int j1,
Matrix X)```
Set a submatrix.

Parameters:
`r` - Array of row indices.
`j0` - Initial column index
`j1` - Final column index
`X` - A(r(:),j0:j1)
Throws:
`java.lang.ArrayIndexOutOfBoundsException` - Submatrix indices

### setMatrix

```public void setMatrix(int i0,
int i1,
int[] c,
Matrix X)```
Set a submatrix.

Parameters:
`i0` - Initial row index
`i1` - Final row index
`c` - Array of column indices.
`X` - A(i0:i1,c(:))
Throws:
`java.lang.ArrayIndexOutOfBoundsException` - Submatrix indices

### transpose

`public Matrix transpose()`
Matrix transpose.

Returns:
A'

### norm1

`public double norm1()`
One norm

Returns:
maximum column sum.

### normInf

`public double normInf()`
Infinity norm

Returns:
maximum row sum.

### normF

`public double normF()`
Frobenius norm

Returns:
sqrt of sum of squares of all elements.

### uminus

`public Matrix uminus()`
Unary minus

Returns:
-A

### plus

`public Matrix plus(Matrix B)`
C = A + B

Parameters:
`B` - another matrix
Returns:
A + B

### plusEquals

`public Matrix plusEquals(Matrix B)`
A = A + B

Parameters:
`B` - another matrix
Returns:
A + B

### minus

`public Matrix minus(Matrix B)`
C = A - B

Parameters:
`B` - another matrix
Returns:
A - B

### minusEquals

`public Matrix minusEquals(Matrix B)`
A = A - B

Parameters:
`B` - another matrix
Returns:
A - B

### arrayTimes

`public Matrix arrayTimes(Matrix B)`
Element-by-element multiplication, C = A.*B

Parameters:
`B` - another matrix
Returns:
A.*B

### arrayTimesEquals

`public Matrix arrayTimesEquals(Matrix B)`
Element-by-element multiplication in place, A = A.*B

Parameters:
`B` - another matrix
Returns:
A.*B

### arrayRightDivide

`public Matrix arrayRightDivide(Matrix B)`
Element-by-element right division, C = A./B

Parameters:
`B` - another matrix
Returns:
A./B

### arrayRightDivideEquals

`public Matrix arrayRightDivideEquals(Matrix B)`
Element-by-element right division in place, A = A./B

Parameters:
`B` - another matrix
Returns:
A./B

### arrayLeftDivide

`public Matrix arrayLeftDivide(Matrix B)`
Element-by-element left division, C = A.\B

Parameters:
`B` - another matrix
Returns:
A.\B

### arrayLeftDivideEquals

`public Matrix arrayLeftDivideEquals(Matrix B)`
Element-by-element left division in place, A = A.\B

Parameters:
`B` - another matrix
Returns:
A.\B

### times

`public Matrix times(double s)`
Multiply a matrix by a scalar, C = s*A

Parameters:
`s` - scalar
Returns:
s*A

### timesEquals

`public Matrix timesEquals(double s)`
Multiply a matrix by a scalar in place, A = s*A

Parameters:
`s` - scalar
Returns:
replace A by s*A

### times

`public Matrix times(Matrix B)`
Linear algebraic matrix multiplication, A * B

Parameters:
`B` - another matrix
Returns:
Matrix product, A * B
Throws:
`java.lang.IllegalArgumentException` - Matrix inner dimensions must agree.

### trace

`public double trace()`
Matrix trace.

Returns:
sum of the diagonal elements.

### random

```public static Matrix random(int m,
int n)```
Generate matrix with random elements

Parameters:
`m` - Number of rows.
`n` - Number of colums.
Returns:
An m-by-n matrix with uniformly distributed random elements.

### identity

```public static Matrix identity(int m,
int n)```
Generate identity matrix

Parameters:
`m` - Number of rows.
`n` - Number of colums.
Returns:
An m-by-n matrix with ones on the diagonal and zeros elsewhere.

### print

```public void print(int w,
int d)```
Print the matrix to stdout. Line the elements up in columns with a Fortran-like 'Fw.d' style format.

Parameters:
`w` - Column width.
`d` - Number of digits after the decimal.

### print

```public void print(java.io.PrintWriter output,
int w,
int d)```
Print the matrix to the output stream. Line the elements up in columns with a Fortran-like 'Fw.d' style format.

Parameters:
`output` - Output stream.
`w` - Column width.
`d` - Number of digits after the decimal.

### print

```public void print(java.text.NumberFormat format,
int width)```
Print the matrix to stdout. Line the elements up in columns. Use the format object, and right justify within columns of width characters. Note that is the matrix is to be read back in, you probably will want to use a NumberFormat that is set to US Locale.

Parameters:
`format` - A Formatting object for individual elements.
`width` - Field width for each column.
`DecimalFormat.setDecimalFormatSymbols(java.text.DecimalFormatSymbols)`

### print

```public void print(java.io.PrintWriter output,
java.text.NumberFormat format,
int width)```
Print the matrix to the output stream. Line the elements up in columns. Use the format object, and right justify within columns of width characters. Note that is the matrix is to be read back in, you probably will want to use a NumberFormat that is set to US Locale.

Parameters:
`output` - the output stream.
`format` - A formatting object to format the matrix elements
`width` - Column width.
`DecimalFormat.setDecimalFormatSymbols(java.text.DecimalFormatSymbols)`

```public static Matrix read(java.io.BufferedReader input)
throws java.io.IOException```
Read a matrix from a stream. The format is the same the print method, so printed matrices can be read back in (provided they were printed using US Locale). Elements are separated by whitespace, all the elements for each row appear on a single line, the last row is followed by a blank line.

Parameters:
`input` - the input stream.
Throws:
`java.io.IOException`

### checkMatrixDimensions

`private void checkMatrixDimensions(Matrix B)`
Check if size(A) == size(B)