interpprev: Interpolation Using the Previous Value

Description

These functions provide an interpolation mechanism for objects of class lgtdl. The AsIs method is the vectorized version.

Usage

interpprev(x, ...)
"interpprev"(x, time, cov, ...)
"interpprev"(x, ...)

Arguments

x is either an object of class lgtdl or of class AsIs. It is the object on which interpolation is to be performed.

time

A vector of times at which interpolation is requested.

cov

The name of the covariate on which interpolation is requested. It is only required if x has more than one covariate.

...

Ignored.

Value

interpprev.lgtdl returns a numeric vector of the interpolated values of the covariate at the time(s) specified by time. interpprev.AsIs returns a vector of interpolated values of the covariate. In this case the vector contains one value for each element x. time must be either the same length as x or of length one. In the latter case all interpolations are done at that time.

Details

If objects of class lgtdl are inserted into a data frame they become a vector with class AsIs. In order to operate on these we provide a method for that class. The method is simply a vectorized version.

Examples

Run this code

  x1<-data.frame(time=c(1,3,5), cov=c(4,6,8))
  x2<-data.frame(time=c(11,13,15), interest=c(66,45,88))
  x1<-as.lgtdl(x1)
  x2<-as.lgtdl(x2)
  interpprev(x1, c(2,4))
  interpprev(x2, c(12, 14))