Rcapture (version 1.2-1)

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, meanning that in the output matrix the unobserved capture histories having a 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.

Details

This function is useful when using an open population model to analyse a robust design data set. It can be used to reduce the data set to one observation per primary period. The observation is one for a unit caught at least once during the period and zero for 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 in argument to an model fiting 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)