weka.core

Class AttributeExpression

java.lang.Object

weka.core.AttributeExpression

All Implemented Interfaces:

java.io.Serializable, RevisionHandler

public class AttributeExpression
extends java.lang.Object
implements java.io.Serializable, RevisionHandler

A general purpose class for parsing mathematical expressions involving attribute values. Values can be provided in an array or in an Instance. Values are accessed in the expression by prefixing their index (starting at 1) with the character 'a'.

 Example expression: a1^2*a5/log(a7*4.0) 

Supported opperators: +, -, *, /, ^, log, abs, cos, exp, sqrt, floor, ceil, rint, tan, sin, (, ).

Version:

$Revision: 5989 $

Author:

Mark Hall

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
AttributeExpression()

Method Summary

Modifier and Type	Method and Description
void	convertInfixToPostfix(java.lang.String infixExp) Converts a string containing a mathematical expression in infix form to postfix form.
void	evaluateExpression(double[] vals) Evaluate the expression using the supplied array of attribute values.
double	evaluateExpression(Instance instance) Evaluate the expression using the supplied Instance.
java.lang.String	getPostFixExpression() Return the postfix expression
java.lang.String	getRevision() Returns the revision string.
java.lang.String	toString()

Methods inherited from class java.lang.Object

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

Constructor Detail

AttributeExpression

public AttributeExpression()

Method Detail

convertInfixToPostfix

public void convertInfixToPostfix(java.lang.String infixExp)
                           throws java.lang.Exception

Converts a string containing a mathematical expression in infix form to postfix form. The result is stored in the vector m_postfixExpVector

Parameters:

infixExp - the infix expression to convert

Throws:

java.lang.Exception - if something goes wrong during the conversion

evaluateExpression

public double evaluateExpression(Instance instance)
                          throws java.lang.Exception

Evaluate the expression using the supplied Instance. Assumes that the infix expression has been converted to postfix and stored in m_postFixExpVector

Parameters:

instance - the Instance containing values to apply the expression to

Throws:

java.lang.Exception - if something goes wrong

evaluateExpression

public void evaluateExpression(double[] vals)
                        throws java.lang.Exception

Evaluate the expression using the supplied array of attribute values. The result is stored in the last element of the array. Assumes that the infix expression has been converted to postfix and stored in m_postFixExpVector

Parameters:

vals - the values to apply the expression to

Throws:

java.lang.Exception - if something goes wrong

getPostFixExpression

public java.lang.String getPostFixExpression()

Return the postfix expression

Returns:

the postfix expression as a String

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

getRevision

public java.lang.String getRevision()

Returns the revision string.

Specified by:

getRevision in interface RevisionHandler

Returns:

the revision