R: Construct Possibly Sparse Design or Model Matrices

model.Matrix {MatrixModels}

R Documentation

Construct Possibly Sparse Design or Model Matrices

Description

model.Matrix creates design matrix, very much like the standard R function model.matrix, however returning a dense or sparse object of class modelMatrix.

Usage

model.Matrix(object, data = environment(object),
             contrasts.arg = NULL, xlev = NULL,
             sparse = FALSE, drop.unused.levels = FALSE, ...)

Arguments

`object`	an object of an appropriate class. For the default method, a model formula or a `terms` object.
`data`	a data frame created with `model.frame`. If another sort of object, `model.frame` is called first.
`contrasts.arg`	A list, whose entries are values (numeric matrices or character strings naming functions) to be used as replacement values for the `contrasts` replacement function and whose names are the names of columns of `data` containing `factor`s.
`xlev`	to be used as argument of `model.frame` if `data` has no `"terms"` attribute.
`sparse`	logical indicating if the result should be sparse (of class `sparseModelMatrix`), using `sparse.model.matrix()` (package Matrix).
`drop.unused.levels`	used only when `sparse` is TRUE: Should factors have unused levels dropped? (This used to be true, implicitly in the first versions up to July 2010; the default has been changed for compatibility with R's standard (dense) `model.matrix()`.
`...`	further arguments passed to or from other methods.

Details

model.Matrix() is a simple wrapper either (sparse = FALSE) around the traditional model.matrix() returning a "ddenseModelMatrix", or (sparse = TRUE) around sparse.model.matrix(), returning a "dsparseModelMatrix" object.

model.Matrix creates a design matrix from the description given in terms(object), using the data in data which must supply variables with the same names as would be created by a call to model.frame(object) or, more precisely, by evaluating attr(terms(object), "variables").

For more details, see model.matrix.

Value

an object inheriting from class modelMatrix, by default, ddenseModelMatrix.

Examples

data(CO2, package="datasets")
class(sm <- model.Matrix(~ 0+Type*Treatment, data=CO2, sparse=TRUE))
class(dm <- model.Matrix(~ 0+Type*Treatment, data=CO2, sparse=FALSE))
stopifnot(dim(sm) == c(84,4), dim(sm) == dim(dm), all(sm == dm))

[Package MatrixModels version 0.4-1 Index]