R: Find the Most Recent Value of a Time-varying Covariate Before...

gettvc {rmutil} | R Documentation

## Find the Most Recent Value of a Time-varying Covariate Before Each Observed Response

### Description

`gettvc` finds the most recent value of a time-varying covariate before each observed response and possibly adds them to a list of other time-varying covariates. It compares the times of response observations with those of time-varying covariates to find the most recent observed time-varying covariate for each response. These are either placed in a new object of class, `tvcov`, added to an already existing list of matrices containing other time-varying covariates and a new object of class, `tvcov`, created, or added to an existing object of class, `tvcov`.

If there are response observation times before the first covariate time, the covariate for these times is set to zero.

### Usage

    gettvc(response, times=NULL, tvcov=NULL, tvctimes=NULL,
    	oldtvcov=NULL, ties=TRUE)

### Arguments

`response` | A list of two column matrices with response values and times for each individual, one matrix or dataframe of response values, or an object of class, `response` (created by `restovec`).
`times` | When `response` is a matrix, a vector of possibly unequally spaced times for the response, when they are the same for all individuals or a matrix of times. Not necessary if equally spaced.
`tvcov` | A list of two column matrices with time-varying covariate values and corresponding times for each individual or one matrix or dataframe of such covariate values. Times need not be the same as for responses.
`tvctimes` | When the time-varying covariate is a matrix, a vector of possibly unequally spaced times for the covariate, when they are the same for all individuals or a matrix of times. Not necessary if equally spaced.
`oldtvcov` | A list of matrices with time-varying covariate values, observed at the event times in `response`, for each individual, or an object of class, `tvcov`. If not provided, a new object is created.
`ties` | If TRUE, when the response and covariate times are identical, the response depends on that new value (as in observational studies); if FALSE, only the next response depends on that value (for example, if the covariate is a new treatment just applied at that time).

### Value

An object of class, `tvcov`, is returned containing the new time-varying covariate and, possibly, those in `oldtvcov`.

### Author(s)

J.K. Lindsey and D.F. Heitjan

### See Also

`read.list`, `restovec`, `tvctomat`.

### Examples

    ## Not run:
    y <- matrix(rnorm(20), ncol=5)
    resp <- restovec(y, times=c(1,3,6,10,15))
    z <- matrix(rpois(20,5),ncol=5)
    z
    # create a new time-varying covariate object for the response
    newtvc <- gettvc(resp, tvcov=z, tvctimes=c(1,2,5,12,14))
    covariates(newtvc)
    # add another time-varying covariate to the object
    z2 <- matrix(rpois(20,5),ncol=5)
    z2
    newtvc2 <- gettvc(resp, tvcov=z2, tvctimes=c(0,4,5,12,16), oldtvc=newtvc)
    covariates(newtvc2)

    ## End(Not run)

[Package rmutil version 1.1.3 Index]