epi.offset {epiR}

Create offset vector

Description

Creates an offset vector based on a list.

Usage

epi.offset(id.names)

Arguments

id.names

a list identifying the [location] of each case. This must be a factor.

Details

This function is useful for supplying spatial data to WinBUGS.

Value

A vector of length (1 + length of id). The first element of the offset vector is 1, corresponding to the position at which data for the first factor appears in id. The second element of the offset vector corresponds to the position at which the second factor appears in id and so on. The last element of the offset vector corresponds to the length of the id list.

References

Bailey TC, Gatrell AC (1995). Interactive Spatial Data Analysis. Longman Scientific & Technical. London.

Langford IH (1994). Using empirical Bayes estimates in the geographical analysis of disease risk. Area 26: 142 - 149.

Examples

## EXAMPLE 1:
dat.v01 <- c(1,1,1,2,2,2,2,3,3,3)
dat.v01 <- as.factor(dat.v01)

dat.ofs01 <- epi.offset(dat.v01)
dat.ofs01
## [1] 1 4 8 10