TABLE OF CONTENTS

initialization/makeas [ Functions ]

NAME

    makeas --- construct discretization

FUNCTION

Split the range of event times into intervals, during which the baseline hazard is assumed constant.

SYNOPSIS

414 makeas <- function(agdata, K, alternating = FALSE)

INPUTS

    agdata         a data frame in Anderson-Gill format
    K              vector the number of breakpoints for each stratum
    alternating    boolean indicating episodic data

OUTPUTS

    as             matrix of size max(r) x max(K)+1 containing
                   discretization breakpoints for each stratum

SOURCE

417 {
418     # get number of strata
419     rmax <- max(agdata$r)
420     
421     # extract the portion of agdata containing events
422     agdatatemp <- agdata[agdata$delta == 1 | 
423         c(diff(agdata$i * 1000 + agdata$j) != 0, TRUE), ]
424     if(!alternating) {
425         agdatatemp$start[ - 1] <- agdatatemp$stop[ - length(agdatatemp$stop)]
426         agdatatemp$start[c(1, diff(agdatatemp$i * 1000 + agdatatemp$j)) != 0] <- 0
427     }
428 
429     # Initialize matrices.
430     as <- matrix(0, rmax, max(K) + 1)
431     for(r in 1:rmax){
432         # Extract the set of event times and death times for each stratum
433         eventtimes <- c(0, sort(unique((agdatatemp$stop - 
434             agdatatemp$start)[agdatatemp$r == r & agdatatemp$delta == 1])))
435         maxtime <- max((agdatatemp$stop - agdatatemp$start)[agdatatemp$r == r])+.001
436         # Compute the set of breakpoints as quantiles, and fill in the rest 
437         # of the matrix with the maximum value.
438         as[r, 1:(K[r] + 1)] <- quantile(c(eventtimes, maxtime), 
439             seq(from = 0, to = 1, length = K[r] + 1))
440         if(K[r] < max(K)) as[r, (K[r] + 2):max(K + 1)] <- maxtime
441     }
442     return(as)    
443 }