| java.lang.Object
 weka.classifiers.CostMatrix
| CostMatrix | | public class CostMatrix implements Serializable(Code) | | Class for storing and manipulating a misclassification cost matrix.
The element at position i,j in the matrix is the penalty for classifying
an instance of class j as class i. Cost values can be fixed or
computed on a per-instance basis (cost sensitive evaluation only)
from the value of an attribute or an expression involving
attribute(s).
author:
Mark Hall
author:
Richard Kirkby (rkirkby@cs.waikato.ac.nz)
version:
$Revision: 1.15 $ |
| Constructor Summary | |
| public | CostMatrix(int numOfClasses)
Creates a default cost matrix of a particular size. | | public | CostMatrix(CostMatrix toCopy)
Creates a cost matrix that is a copy of another. | | public | CostMatrix(Reader reader)
Reads a matrix from a reader. |
| Method Summary | |
| public Instances | applyCostMatrix(Instances data, Random random)
Applies the cost matrix to a set of instances. | | public double[] | expectedCosts(double[] classProbs)
Calculates the expected misclassification cost for each possible class value,
given class probability estimates. | | public double[] | expectedCosts(double[] classProbs, Instance inst)
Calculates the expected misclassification cost for each possible class value,
given class probability estimates. | | final public Object | getCell(int rowIndex, int columnIndex)
Return the contents of a particular cell. | | final public double | getElement(int rowIndex, int columnIndex)
| | final public double | getElement(int rowIndex, int columnIndex, Instance inst)
Return the value of a cell as a double. | | public double | getMaxCost(int classVal)
Gets the maximum cost for a particular class value.
Parameters:
classVal - the class value. | | public double | getMaxCost(int classVal, Instance inst)
Gets the maximum cost for a particular class value.
Parameters:
classVal - the class value. | | public void | initialize()
| | public void | normalize()
Normalizes the matrix so that the diagonal contains zeros. | | public int | numColumns()
| | public int | numRows()
| | public static Matrix | parseMatlab(String matlab)
creates a matrix from the given Matlab string. | | public void | readOldFormat(Reader reader)
Loads a cost matrix in the old format from a reader. | | final public void | setCell(int rowIndex, int columnIndex, Object value)
| | final public void | setElement(int rowIndex, int columnIndex, double value)
| | public int | size()
| | public String | toMatlab()
converts the Matrix into a single line Matlab string: matrix is enclosed
by parentheses, rows are separated by semicolon and single cells by
blanks, e.g., [1 2; 3 4]. | | public String | toString()
Converts a matrix to a string. | | public void | write(Writer w)
Writes out a matrix. |
| FILE_EXTENSION | | public static String FILE_EXTENSION(Code) | | The deafult file extension for cost matrix files
|
| CostMatrix | | public CostMatrix(int numOfClasses)(Code) | | Creates a default cost matrix of a particular size.
All diagonal values will be 0 and all non-diagonal values 1.
Parameters:
numOfClasses - the number of classes that the cost matrix holds. |
| CostMatrix | | public CostMatrix(CostMatrix toCopy)(Code) | | Creates a cost matrix that is a copy of another.
Parameters:
toCopy - the matrix to copy. |
| CostMatrix | | public CostMatrix(Reader reader) throws Exception(Code) | | Reads a matrix from a reader. The first line in the file should
contain the number of rows and columns. Subsequent lines
contain elements of the matrix.
(FracPete: taken from old weka.core.Matrix class)
Parameters:
reader - the reader containing the matrix
throws:
Exception - if an error occurs
See Also: CostMatrix.write(Writer) |
| applyCostMatrix | | public Instances applyCostMatrix(Instances data, Random random) throws Exception(Code) | | Applies the cost matrix to a set of instances. If a random number generator is
supplied the instances will be resampled, otherwise they will be rewighted.
Adapted from code once sitting in Instances.java
Parameters:
data - the instances to reweight.
Parameters:
random - a random number generator for resampling, if null then instances arerewighted. a new dataset reflecting the cost of misclassification.
exception:
Exception - if the data has no class or the matrix in inappropriate. |
| expectedCosts | | public double[] expectedCosts(double[] classProbs) throws Exception(Code) | | Calculates the expected misclassification cost for each possible class value,
given class probability estimates.
Parameters:
classProbs - the class probability estimates. the expected costs.
exception:
Exception - if the wrong number of class probabilities is supplied. |
| expectedCosts | | public double[] expectedCosts(double[] classProbs, Instance inst) throws Exception(Code) | | Calculates the expected misclassification cost for each possible class value,
given class probability estimates.
Parameters:
classProbs - the class probability estimates.
Parameters:
inst - the current instance for which the class probabilitesapply. Is used for computing any non-fixed cost values. the expected costs.
exception:
Exception - if something goes wrong |
| getCell | | final public Object getCell(int rowIndex, int columnIndex)(Code) | | Return the contents of a particular cell. Note: this
method returns the Object stored at a particular cell.
Parameters:
rowIndex - the row
Parameters:
columnIndex - the column the value at the cell |
| getElement | | final public double getElement(int rowIndex, int columnIndex) throws Exception(Code) | | Return the value of a cell as a double (for legacy code)
Parameters:
rowIndex - the row
Parameters:
columnIndex - the column the value at a particular cell as a double
exception:
Exception - if the value is not a double |
| getElement | | final public double getElement(int rowIndex, int columnIndex, Instance inst) throws Exception(Code) | | Return the value of a cell as a double. Computes the
value for non-fixed costs using the supplied Instance
Parameters:
rowIndex - the row
Parameters:
columnIndex - the column the value from a particular cell
exception:
Exception - if something goes wrong |
| getMaxCost | | public double getMaxCost(int classVal) throws Exception(Code) | | Gets the maximum cost for a particular class value.
Parameters:
classVal - the class value. the maximum cost.
exception:
Exception - if cost matrix contains non-fixedcosts |
| getMaxCost | | public double getMaxCost(int classVal, Instance inst) throws Exception(Code) | | Gets the maximum cost for a particular class value.
Parameters:
classVal - the class value. the maximum cost.
exception:
Exception - if cost matrix contains non-fixedcosts |
| initialize | | public void initialize()(Code) | | Initializes the matrix
|
| normalize | | public void normalize()(Code) | | Normalizes the matrix so that the diagonal contains zeros.
|
| numColumns | | public int numColumns()(Code) | | Same as size
the number of columns |
| numRows | | public int numRows()(Code) | | Same as size
the number of rows |
| parseMatlab | | public static Matrix parseMatlab(String matlab) throws Exception(Code) | | creates a matrix from the given Matlab string.
Parameters:
matlab - the matrix in matlab format the matrix represented by the given string |
| readOldFormat | | public void readOldFormat(Reader reader) throws Exception(Code) | | Loads a cost matrix in the old format from a reader. Adapted from code once sitting
in Instances.java
Parameters:
reader - the reader to get the values from.
exception:
Exception - if the matrix cannot be read correctly. |
| setCell | | final public void setCell(int rowIndex, int columnIndex, Object value)(Code) | | Set the value of a particular cell in the matrix
Parameters:
rowIndex - the row
Parameters:
columnIndex - the column
Parameters:
value - the value to set |
| setElement | | final public void setElement(int rowIndex, int columnIndex, double value)(Code) | | Set the value of a cell as a double
Parameters:
rowIndex - the row
Parameters:
columnIndex - the column
Parameters:
value - the value (double) to set |
| size | | public int size()(Code) | | The number of rows (and columns)
the size of the matrix |
| toMatlab | | public String toMatlab()(Code) | | converts the Matrix into a single line Matlab string: matrix is enclosed
by parentheses, rows are separated by semicolon and single cells by
blanks, e.g., [1 2; 3 4].
the matrix in Matlab single line format |
| toString | | public String toString()(Code) | | Converts a matrix to a string.
(FracPete: taken from old weka.core.Matrix class)
the converted string |
| write | | public void write(Writer w) throws Exception(Code) | | Writes out a matrix. The format can be read via the
CostMatrix(Reader) constructor.
(FracPete: taken from old weka.core.Matrix class)
Parameters:
w - the output Writer
throws:
Exception - if an error occurs |
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