magpie.attributes.expanders

Class FunctionExpander

java.lang.Object

magpie.attributes.expanders.BaseAttributeExpander

magpie.attributes.expanders.FunctionExpander

All Implemented Interfaces:

java.io.Serializable, Citable, Options

public class FunctionExpander
extends BaseAttributeExpander
implements Citable

Generates new attributes that are arbitrary functions of other attributes. The idea for this class was based on work by L. Ghiringhelli et al.

To define a function used to generate new attributes, simply write out a expression with the variables surrounded by #{}'s (e.g., (#{x} + #{y}/#{x})). This expander will substitute the all possible combinations of attributes for each of those variables. If you would like to generate all permutations of attributes in a specific formula, write out all possible orders of variables into that formula (ex: both #{x}/#{y} and #{y}/#{x})

Variables names that start with "r:" can be used to allow only certain attributes. These variables are expected to be of the format "r:[name],[regex]" where [name] is a unique name and [regex] is the regular expression used to decide whether a variable will be used to decide whether an attribute will be used in the function. This classes uses the Matcher.find() to test whether an attribute name contains a substring matching the regular expression. For example, "r:x,*" would match all attributes and "r:x,^a.*z$" would match only attributes that start with a and end with z. The formula "#{r:x,*}*#{r:y,^time$}" would multiple all attributes with the attribute named "time". Note, this will generate all permutations of attributes for each variable.

Examples

• #{x}^2 : Square all attributes
• #{r:x,^a}^2 : Square all attributes beginning with "a"
• #{r:x,a}^2 : Square all attributes containing an "a"
• #{x}*#{y} : Multiply each combination of attributes
• #{r:x,[0-9]}*#{y} : Multiply any attribute containing a number with all other attributes

Usage: "<function #1>" ["<function #2>"] [<...>]
function: Function describing a new combination of attributes.
Functions should follow the syntax outlined in the Javadoc

See Also:

ParsedFunction, Serialized Form

Constructor Summary

Constructors

Constructor and Description
FunctionExpander()

Method Summary

Modifier and Type	Method and Description
void	addNewFunction(java.lang.String function) Add a new function to be used for expansion
void	clearFunctionList() Clear list of functions used to generate new attributes.
void	expand(Dataset Data) Generate new attributes based on the attributes already in Dataset
protected java.util.List<int[]>	generateCombinations(java.lang.String[] attributeNames, ParsedFunction function) Compute all acceptable combinations of attributes for a
java.util.List<org.apache.commons.lang3.tuple.Pair<java.lang.String,Citation>>	getCitations() Return a list of citations for this object and any underlying objects.
java.lang.String	printUsage() Print out required format for options.
void	setOptions(java.util.List<java.lang.Object> Options) Set any options for this object.

Methods inherited from class java.lang.Object

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

Constructor Detail

FunctionExpander

public FunctionExpander()

Method Detail

setOptions

public void setOptions(java.util.List<java.lang.Object> Options)
                throws java.lang.Exception

Description copied from interface: Options

Set any options for this object. If parsing the options fails, return an Exception with the usage as its message.

Specified by:

setOptions in interface Options

Parameters:

Options - Array of options as Objects - can be null

Throws:

java.lang.Exception - if problem with inputs

printUsage

public java.lang.String printUsage()

Description copied from interface: Options

Print out required format for options. For consistency, should start with "Usage: ".

Specified by:

printUsage in interface Options

Returns:

Usage for this function

clearFunctionList

public void clearFunctionList()

Clear list of functions used to generate new attributes.

addNewFunction

public void addNewFunction(java.lang.String function)
                    throws java.lang.Exception

Add a new function to be used for expansion

Parameters:

function - Function to be parsed

Throws:

java.lang.Exception

expand

public void expand(Dataset Data)

Description copied from class: BaseAttributeExpander

Generate new attributes based on the attributes already in Dataset

Specified by:

expand in class BaseAttributeExpander

Parameters:

Data - Dataset to be expanded

generateCombinations

protected java.util.List<int[]> generateCombinations(java.lang.String[] attributeNames,
                                                     ParsedFunction function)

Compute all acceptable combinations of attributes for a

Parameters:

attributeNames -

function -

Returns:

getCitations

public java.util.List<org.apache.commons.lang3.tuple.Pair<java.lang.String,Citation>> getCitations()

Description copied from interface: Citable

Return a list of citations for this object and any underlying objects.

Specified by:

getCitations in interface Citable

Returns:

List of pairs: [Reason for Citation], [Citation]