NDarroch {recapr}

Spatially or Temporally Stratified Abundance Est (Darroch)

Description

Computes abundance estimates and associated variance in the event of spatial or temporal stratification, or in any stratification in which individuals can move between strata. Marking (event 1) and recapture (event 2) strata do not need to be the same.

Inputs are vectors of total event 1 and 2 sample sizes, and either vectors of event 1 and 2 strata corresponding to each recaptured individual, or a matrix of total number of recaptures for each combination of event 1 and event 2 strata.

Implementation is currently using Darroch's method, and will only accept non-singular input matrices.

Usage

NDarroch(
  n1counts,
  n2counts,
  m2strata1 = NULL,
  m2strata2 = NULL,
  stratamat = NULL
)

Arguments

n1counts

A vector of the total sample sizes in the first event, by strata. For example, setting n1counts=c(20,30,40) would imply 20 individuals captured and marked in stratum 1, 30 in stratum 2, and 40 in stratum 3.

n2counts

A vector of the total sample sizes in the second event, by strata.

m2strata1

A vector of the first-event stratum membership of each recaptured individual. Only values 1, 2, 3, ... are allowed. May be used together with m2strata2 instead of stratamat.

m2strata2

A vector of the second-event stratum membership of each recaptured individual. Only values 1, 2, 3, ... are allowed. May be used together with m2strata1 instead of stratamat.

stratamat

A matrix specifying the number of recaptures in each combination of event 1 and event 2 strata, with rows corresponding to event 1 strata and columns corresponding to event 2 strata. May be used instead of m2strata1 and m2strata2.

Value

A numeric list, giving the strata matrix if originally given in vector form, abundance estimates and standard errors by event 1 and event 2 strata, and the total abundance estimate and standard error.

Author(s)

Matt Tyers

References

Darroch, J.N. (1961). The two-sample capture-recapture census when tagging and sampling are stratified. Biometrika 48, 241-60.

See Also

consistencytest

Examples

mat <- matrix(c(59,30,1,45,280,38,0,42,25), nrow=3, ncol=3, byrow=TRUE)

NDarroch(n1counts=c(484,1468,399), n2counts=c(847,6616,2489), stratamat=mat)