Package smile.feature.selection

Class SumSquaresRatio

java.lang.Object

smile.feature.selection.SumSquaresRatio

All Implemented Interfaces:

Comparable<SumSquaresRatio>

public class SumSquaresRatio
extends Object
implements Comparable<SumSquaresRatio>

The ratio of between-groups to within-groups sum of squares is a univariate feature ranking metric, which can be used as a feature selection criterion for multi-class classification problems. For each variable j, this ratio is BSS(j) / WSS(j) = ΣI(y_i = k)(x_kj - x_·j)² / ΣI(y_i = k)(x_ij - x_kj)²; where x_·j denotes the average of variable j across all samples, x_kj denotes the average of variable j across samples belonging to class k, and x_ij is the value of variable j of sample i. Clearly, features with larger sum squares ratios are better for classification.

References

1. S. Dudoit, J. Fridlyand and T. Speed. Comparison of discrimination methods for the classification of tumors using gene expression data. J Am Stat Assoc, 97:77-87, 2002.

Field Summary

Fields

Modifier and Type	Field	Description
final String	feature	The feature name.
final double	ssr	Sum squares ratio.

Constructor Summary

Constructors

Constructor	Description
SumSquaresRatio(String feature, double ssr)	Constructor.

Method Summary

Modifier and Type	Method	Description
int	compareTo(SumSquaresRatio other)
static SumSquaresRatio[]	fit(DataFrame data, String clazz)	Calculates the sum squares ratio of numeric variables.
String	toString()

Methods inherited from class java.lang.Object

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

Field Details

feature

public final String feature

The feature name.

ssr

public final double ssr

Sum squares ratio.

Constructor Details

SumSquaresRatio

public SumSquaresRatio(String feature,
 double ssr)

Constructor.

Parameters:

feature - The feature name.

ssr - Sum squares ratio.

Method Details

compareTo

public int compareTo(SumSquaresRatio other)

Specified by:

compareTo in interface Comparable<SumSquaresRatio>

toString

public String toString()

Overrides:

toString in class Object

fit

public static SumSquaresRatio[] fit(DataFrame data,
 String clazz)

Calculates the sum squares ratio of numeric variables.

Parameters:

data - the data frame of the explanatory and response variables.

clazz - the column name of class labels.

Returns:

the sum squares ratio.