# coord.hyp.basis: Internal function to find the basis of a subspace In dr: Methods for Dimension Reduction for Regression

## Description

If a dimension reduction object has p dimension, returns a p \times r matrix whose columns space a subspace specified by a formula.

## Usage

 1 coord.hyp.basis(object, spec, which = 1) 

## Arguments

 object A dr object spec A one-sided formula, see below which either +1 or -1; see below

## Details

The workings of this function is best explained by an example. Suppose the dr object was created with the formula y~x1+x2+x3+x4, so we have p=4 predictors. A matrix that spans the subspace of R^4 specified by Span(x1,x2,x3,x4) is simply the identity matrix of order 4.

This function will return a subset of the columns of this identity matrix, as determined by spec. For example, if spec = ~.-(x3+x4), the function returns the columns corresponding to x1 and x2 if which=+1 or the columns corresponding to x3 and x4 if which=-1. Similarly, if spec=~x1+x2, the same matrices will be returned.

## Value

A matrix corresponding to the value of spec and which given.

## Author(s)

Sanford Weisberg, sandy@stat.umn.edu

dr.coordinate.test
 1 2 3 4 5 data(ais) s1 <- dr(LBM~log(Ht)+log(Wt)+log(RCC)+log(WCC)+log(Hc)+log(Hg), data=ais,method="sir") coord.hyp.basis(s1,~.-log(Wt)-log(Hg))