lfe (version 1.0-418)

demeanlist: Centre vectors on multiple groups

Description

Uses the method of alternating projections to centre a (model) matrix on multiple groups, as specified by a list of factors.

Usage

demeanlist(mtx,fl,icpt=0,eps=getOption('lfe.eps'),threads=getOption('lfe.threads'))

Arguments

mtx

matrix whose columns form vectors to be group-centred. mtx may also be a list of vectors.

fl

list of factors defining the grouping structure

icpt

the position of the intercept, this column is removed from the result

eps

a tolerance for the centering

threads

an integer specifying the number of threads to use

Value

• If mtx is a matrix, a matrix of the same shape, possibly with the column icpt deleted. If mtx is a list of vectors, a list of the same length is returned.

Examples

## create a 45x3 matrix
mtx <- matrix(rnorm(45),15,3)

## a list of factors
fl <- list(g1=factor(sample(2,nrow(mtx),replace=TRUE)),
           g2=factor(sample(3,nrow(mtx),replace=TRUE)))

## centre on both means and print result
mtx0 <- demeanlist(mtx,fl)
print(cbind(mtx0,g1=fl[[1]],g2=fl[[2]],comp=compfactor(fl)))

for(i in 1:ncol(mtx0))
   for(n in names(fl))
    cat('col',i,'group',n,'level sums:',tapply(mtx0[,i],fl[[n]],mean),'\n')