split_scale-methods: Center and/or Scale Row-subsets of a Matrix or Matrix-like...

In bbuchsbaum/neuroim2: Data Structures for Brain Imaging Data

Center and/or Scale Row-subsets of a Matrix or Matrix-like Object

Description

This function centers and/or scales the row-subsets of a numeric matrix or matrix-like object.

Usage

split_scale(x, f, center, scale)

## S4 method for signature 'matrix,factor,logical,logical'
split_scale(x, f, center = TRUE, scale = TRUE)

## S4 method for signature 'matrix,factor,missing,missing'
split_scale(x, f)

## S4 method for signature 'DenseNeuroVec,factor,missing,missing'
split_scale(x, f)

## S4 method for signature 'DenseNeuroVec,factor,logical,missing'
split_scale(x, f, center)

## S4 method for signature 'DenseNeuroVec,factor,logical,logical'
split_scale(x, f, center, scale)

Arguments

x	A numeric matrix or matrix-like object.
f	The splitting object, typically a factor or a set of integer indices. Must be equal to the number of rows in the matrix.
center	Should values within each submatrix be centered? If TRUE, the mean is removed from each column of the submatrix.
scale	Should values be scaled? If TRUE, the vector is divided by the standard deviation for each column of the submatrix.

Value

An object of the same class as x, with row-subsets centered and/or scaled according to f.

Examples

M <- matrix(rnorm(1000), 10, 100)
fac <- factor(rep(1:2, each=5))
Ms <- split_scale(M, fac)

## Correctly centered
all(abs(apply(Ms[fac == 1,], 2, mean)) < .000001)
all(abs(apply(Ms[fac == 2,], 2, mean)) < .000001)

## Correctly scaled
all.equal(apply(Ms[fac == 1,], 2, sd), rep(1, ncol(Ms)))
all.equal(apply(Ms[fac == 2,], 2, sd), rep(1, ncol(Ms)))

bbuchsbaum/neuroim2 documentation built on Feb. 26, 2025, 3:49 p.m.