tcctomat: Create a Time-constant, Inter-individual Covariate (tccov) Object

Description

tcctomat creates an object of class, tccov, from a vector or matrix containing time-constant or inter-individual baseline covariates or a model formula. It can also combine two such objects.

Such objects can be printed. Methods are available for extracting the covariates, their names, and the formula: covariates, names, and formula. The method, transform, can transform variables in place or by adding new variables to the object.

To obtain the indexing to expand time-constant or inter-individual covariates to the size of a repeated measurements response, use covind.

Usage

tcctomat(ccov, names=NULL, units=NULL, oldccov=NULL, dataframe=TRUE,
	description=NULL)

Value

Returns an object of class, tccov, containing one matrix or dataframe for the covariates (z$ccov) with one row per individual and possibly the model formula (z$linear).

Arguments

ccov: A vector, matrix, or dataframe containing time-constant or inter-individual baseline covariates with one row per individual, a model formula using vectors of the same size, or an object of class, tccov. In the first two cases, the variables may be factors; if dataframe=FALSE, these are transformed to indicator variables.
units: Optional character vector specifying units of measurements of covariates.
names: The names of the covariates (if the matrix does not have column names).
oldccov: An object of class, tccov, to which ccov is to be added.
dataframe: If TRUE and factor variables are present, the covariates are stored as a dataframe; if FALSE, they are expanded to indicator variables. If no factor variables are present, covariates are always stored as a matrix.
description: An optional named list of character vectors with names of some or all covariates containing their descriptions.

Author

J.K. Lindsey

Examples

Run this code

x1 <- gl(4,1)
print(tcc1 <- tcctomat(~x1))
covariates(tcc1)
covariates(tcc1, name="x12")
tcctomat(x1)
tcctomat(x1, dataframe=FALSE)
x2 <- c(0,0,1,1)
print(tcc2 <- tcctomat(~x2, units="days"))
covariates(tcc2)
print(tcc3 <- tcctomat(~x1+x2))
covariates(tcc3)
covariates(tcc3, names=c("x12","x2"))
formula(tcc3)
names(tcc3)
print(tcc4 <- tcctomat(data.frame(x1,x2), units=c(NA,"days")))
covariates(tcc4)
print(tcc5 <- tcctomat(data.frame(x1,x2), dataframe=FALSE, units=c(NA,"days")))
covariates(tcc5)