Rcapture (version 1.3-1)

periodhist: Merge capture occasions

Description

This function produces a reduced matrix of capture histories from a complete one by merging together some capture occasions. It can also be used to change the format of a capture-recapture data set with complete capture histories: it transforms a data set with one row per captured unit to a data set with one row per capture history followed by its frequency.

Usage

periodhist(X, dfreq=FALSE, vt, drop=TRUE)

Arguments

X

The matrix of the observed capture histories (see Rcapture-package for a description of the accepted formats).

dfreq

A logical. By default FALSE, which means that X has one row per unit. If TRUE, it indicates that the matrix X contains frequencies in its last column.

vt

A vector containing the numbers of capture occasions for each pooled capture occasions. The length of this vector equals the number of capture occasions in the reduced matrix (noted $I$).

drop

A logical, by default TRUE, meaning that in the output matrix the unobserved capture histories (frequency of 0) are omitted. To keep them, drop must be set to FALSE.

Value

• A $2^I-1$ by $I+1$ matrix of all the pooled capture histories, with their observed frequencies. If drop=TRUE (the default), the number of rows of this matrix is in fact $2^I-1$ minus the number of unobserved capture histories.

Details

This function is useful when using an open population model to analyze a robust design data set. It can be used to reduce the data set to one observation per primary period. A one represents a unit caught at least once during the period and a zero a unit never caught. It is also useful for experiments with a large number of capture occasions but a limited number of catches, especially when there is no capture on some occasions. In such cases, one can pool together some capture occasions with the periodhist function. If a data matrix produced by the periodhist function is given as an argument to a Rcapture function, the dfreq argument must be set to TRUE.

References

Baillargeon, S. and Rivest, L.P. (2007) Rcapture: Loglinear models for capture-recapture in R. Journal of Statistical Software, 19(5), http://www.jstatsoft.org/v19/i05.

See Also

openp

Examples

data(mvole)
mvole.op<-periodhist(mvole,vt=rep(5,6))
openp(mvole.op, dfreq=TRUE)