Epi (version 2.34)

bootLexis: Create a bootstrap sample of persons (lex.id) from a Lexis object

Description

lex.id is the identifier of persons in a Lexis object. This is used to sample persons from a Lexis object. If a person is sampled, all records from this persons is transported to the bootstrap sample.

Usage

nid( Lx, … )
# S3 method for Lexis
nid( Lx, by=NULL, … )
bootLexis( Lx, size = NULL, by = NULL, replace=TRUE )

Arguments

Lx

A Lexis object.

…

Parameters passed on to other methods.

size

Numeric. How many persons should be sampled from the Lexis object. Defaults to the number of persons in the Lx, or, if by is given, to the number of persons in each level of by. If by is given size can have length lebgth(unique(by)), to indicate how many are sampled from each level of by.

by

Character. Name of a variable (converted to factor) in the Lexis object.

Bootstrap sampling is done within each level of by.

Calculation of the number of persons (lex.id) is done within each level of by, and a vector returned.

replace

Should persons be sampled by replacement? Setting replace to FALSE enables selecting a random subset of persons from the Lexis object.

Value

A Lexis object of the same structure as the input, with persons bootstrapped. The variable lex.id has values 1,2,...,nid(Lx).

nid counts the number of persons in a Lexis object, possibly by by. If by is given, a named vector is returned.

See Also

Relevel.Lexis,subset.Lexis

Examples

# NOT RUN {
# A small bogus cohort
xcoh <- data.frame( id = c("A", "B", "C"),
                 birth = c("14/07/1952", "01/04/1954", "10/06/1987"),
                 entry = c("04/08/1965", "08/09/1972", "23/12/1991"),
                  exit = c("27/06/1997", "23/05/1995", "24/07/1998"),
                  fail = c(1, 0, 1),
                   sex = c("M","F","M") )
xcoh <- data.frame( id = c("A", "B", "C"),
                 birth = as.Date(c("14/07/1952","01/04/1954","10/06/1987"),format="%d/%m/%Y"),
                 entry = as.Date(c("04/08/1965","08/09/1972","23/12/1991"),format="%d/%m/%Y"),
                  exit = as.Date(c("27/06/1997","23/05/1995","24/07/1998"),format="%d/%m/%Y"),
                  fail = c(1, 0, 1),
                   sex = c("M","F","M") )
xcoh <- cal.yr( xcoh )
Lcoh <- Lexis( entry = list( per=entry ),
                exit = list( per=exit, age=exit-birth ),
         exit.status = fail,
                data = xcoh )
Lx <- Lcoh[sample(1:3,10,replace=TRUE),]
Lx$per <- Lx$per + runif(10,0,10)
Lx$lex.id <- 1:10
Lx <- splitLexis( Lx, breaks=0:10*10, "age" )
Lx
nid( Lx )
nid( Lx, by="sex" )
bootLexis( Lx )
nid( bootLexis( Lx, size=7 ) )
Li <- bootLexis( Lx, by="id" ) # superfluous
L2 <- bootLexis( Lx, by="sex", size=c(2,5) )
nid( L2, by="sex" )
# }