tvctomat: Create a Time-varying, Intra-individual Covariate (tvcov) Object

Description

tvctovmat creates an object of class, tvcov, from a list of matrices with time-varying or intra-individual covariates for each individual or one matrix or dataframe of such covariate values. It can also combine two such objects or add interactions among covariates.

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

Usage

tvctomat(tvcov, names=NULL, units=NULL, interaction=NULL, ccov=NULL,
	oldtvcov=NULL, dataframe=TRUE, description=NULL)

Value

Returns an object of class, tvcov, containing a matrix or dataframe for the covariates (z$tvcov) with one row per response per individual and a vector giving the number of observations per individual (z$nobs).

Arguments

tvcov: Either (1) if unbalanced, a list of matrices or dataframes with time-varying or intra-individual covariate values for each individual (one column per variable), (2) if balanced, one matrix or dataframe of such covariate values (when there is only one such covariate) with dimensions: number of individuals by number of observations/individual, or (3) an object of class, tvcov. In the first two cases, the variables may be factors; if dataframe=FALSE, these are transformed to indicator variables.
names: The names of the time-varying or intra-individual covariates in tvcov (if the matrices do not have column names) or the names of the time-constant covariates for which interactions are to be created.
units: Optional character vector specifying units of measurements of covariates.
interaction: A pair of index numbers or names of variables in tvcov, with that class, for which an interaction is to be added or, if ccov is provided, a set of such names of time-varying or intra-individual covariates for creating interactions with the time-constant covariates.
ccov: Time-constant or inter-individual covariates for which an interaction is to be introduced with time-varying or intra-individual covariates in tvcov.
oldtvcov: An object of class, tvcov, to which tvcov 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

z <- matrix(rpois(20,5),ncol=5)
print(tvc <- tvctomat(z, units="days"))
covariates(tvc)
names(tvc)
v <- data.frame(matrix(rep(c("a","b","c","d","e"),4),ncol=5),stringsAsFactors=TRUE)
print(tvc2 <- tvctomat(v, oldtvc=tvc, units=NA))
covariates(tvc2)
print(tvc3 <- tvctomat(v, oldtvc=tvc, dataframe=FALSE, units=NA))
covariates(tvc3)
print(tvc4 <- tvctomat(tvc2, interaction=c("z","v")))
covariates(tvc4)
x1 <- 1:4
x2 <- gl(4,1)
xx <- tcctomat(data.frame(x1,x2), dataframe=FALSE)
tvctomat(tvc3, interaction="z", ccov=xx)
tvctomat(tvc3, interaction="z", ccov=xx, names="x1")
tvctomat(tvc3, interaction="z", ccov=xx, names=c("x22","x23","x24"))
xx <- tcctomat(data.frame(x1,x2), dataframe=TRUE)
tvctomat(tvc2, interaction="z", ccov=xx)
tvctomat(tvc2, interaction="z", ccov=xx, names="x1")
tvctomat(tvc2, interaction="z", ccov=xx, names="x2")