fwdmv.init {Rfwdmv}R Documentation

Multivariate Forward Search for Ungrouped Data

Description

This function computes a multivariate forward search for ungrouped data. Several diagnostic statistics are monitored during the search: see fwdmv.object. Note that this function is called by fwdmv when no tentative groups are specified. It is recommended that fwdmv be used for all multivariate forward searches.

Usage

fwdmv.init(X, bsb = ellipse.subset, scaled = TRUE)

Arguments

X a matrix or data frame containing the multivariate data set.
bsb a function of two variables: the multivariate data in matrix form X and the number of units in the initial subset size. If bsb= bb.subset the initial susbet is found using robust bivariate boxplots. The default is to use robustly centered ellipses ellipse.subset. Alternatively, the initial subset my be specified directly by providing an integer vector containing the indices of the units to be in the initial subset.
scaled a logical value. If TRUE then scaled Mahalanobis distances are used during the forward search.

Details

This function computes the Forward Search described in chapter 3 of ARC. The initial subset can be specified directly in the argument bsb or computed from the data. By default bsb is a function for computing the initial subset using robustly centered ellipses. Given a subset of m units the next subset is the m+1 units with smallest Mahalanobis distances calculated using the center and covariance matrix estimates of the units currently in the subset. This process is repeated until the subset contains all of the units and several diagnostic statistics are computed for each subset.

Value

aa fwdmv object.

Author(s)

Kjell Konis

References

Atkinson, A. C., Riani, M. and Cerioli, A. (2004) Exploring Multivariate Data with the Forward Search. Springer-Verlag New York.

See Also

fwdmv.object

Examples

data(fondi.dat)
fondi.init <- fwdmv.init(fondi.dat)

data(fondi.dat)
#### find the intial subset using robust bivariate ellipses  
#### start with an initial subset size of 17 units
fondi.init <- fwdmv.init(fondi.dat,bsb=ellipse.subset(fondi.dat,17))

data(fondi.dat)
#### find the intial subset using robust bivariate boxplots and 
#### start with an initial subset size of 17 units and 
fondi.init <- fwdmv.init(fondi.dat,bsb=bb.subset(fondi.dat,17))


[Package Rfwdmv version 0.71 Index]