subselect: ldaHmat – R documentation

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ldaHmat

Total and Between-Group Deviation Matrices in Linear Discriminant Analysis

Description

Computes total and between-group matrices of Sums of Squares and Cross-Product (SSCP) deviations in linear discriminant analysis. These matrices may be used as input to the variable selection search routines anneal, genetic improve or eleaps.

Usage

## Default S3 method:
ldaHmat(x,grouping,...)

## S3 method for class 'data.frame'
ldaHmat(x,grouping,...)

## S3 method for class 'formula'
ldaHmat(formula,data=NULL,...)

Arguments

`x`	A matrix or data frame containing the discriminators for which the SSCP matrix is to be computed.
`grouping`	A factor specifying the class for each observation.
`formula`	A formula of the form `'groups ~ x1 + x2 + ...'` That is, the response is the grouping factor and the right hand side specifies the (non-factor) discriminators.
`data`	Data frame from which variables specified in 'formula' are preferentially to be taken.
`...`	further arguments for the method.

Value

A list with four items:

`mat`	The total SSCP matrix
`H`	The between-groups SSCP matrix
`r`	The expected rank of the H matrix which equals the minimum between the number of discriminators and the number of groups minus one. The true rank of H can be different from r if the discriminators are linearly dependent.
`call`	The function call which generated the output.

Examples

##--------------------------------------------------------------------

## An example with a very small data set. We consider the Iris data
## and three groups, defined by species (setosa, versicolor and
## virginica). 

data(iris)
irisHmat <- ldaHmat(iris[1:4],iris$Species)
irisHmat

##$mat
##             Sepal.Length Sepal.Width Petal.Length Petal.Width
##Sepal.Length   102.168333   -6.322667     189.8730    76.92433
##Sepal.Width     -6.322667   28.306933     -49.1188   -18.12427
##Petal.Length   189.873000  -49.118800     464.3254   193.04580
##Petal.Width     76.924333  -18.124267     193.0458    86.56993

##$H
##             Sepal.Length Sepal.Width Petal.Length Petal.Width
##Sepal.Length     63.21213   -19.95267     165.2484    71.27933
##Sepal.Width     -19.95267    11.34493     -57.2396   -22.93267
##Petal.Length    165.24840   -57.23960     437.1028   186.77400
##Petal.Width      71.27933   -22.93267     186.7740    80.41333

##$r
##[1] 2

##$call
##ldaHmat.data.frame(x = iris[1:4], grouping = iris$Species)

subselect

Selecting Variable Subsets

v0.15.2

GPL (>= 2)

Authors

Jorge Orestes Cerdeira [aut], Pedro Duarte Silva [aut], Jorge Cadima [aut, cre], Manuel Minhoto [aut]

Initial release

2020-03-04