SPAS: Stratified-Petersen Analysis System

The Stratified-Petersen Analysis System (SPAS) is designed to estimate abundance in two-sample capture-recapture experiments where the capture and recaptures are stratified. This is a generalization of the simple Lincoln-Petersen estimator. Strata may be defined in time or in space or both, and the s strata in which marking takes place may differ from the t strata in which recoveries take place. When s=t, SPAS reduces to the method described by Darroch (1961) <doi:10.2307/2332748>. When s<t, SPAS implements the methods described in Plante, Rivest, and Tremblay (1988) <doi:10.2307/2533994>. Schwarz and Taylor (1998) <doi:10.1139/f97-238> describe the use of SPAS in estimating return of salmon stratified by time and geography. A related package, BTSPAS, deals with temporal stratification where a spline is used to model the distribution of the population over time as it passes the second capture location. This is the R-version of the (now obsolete) standalone Windows program available at <>.

Version: 2024.1.31
Imports: MASS, Matrix, msm, numDeriv, plyr, reshape2, TMB (≥ 1.7.15)
LinkingTo: TMB, RcppEigen
Suggests: knitr, rmarkdown
Published: 2024-01-25
DOI: 10.32614/CRAN.package.SPAS
Author: Carl James Schwarz
Maintainer: Carl James Schwarz < at>
License: GPL-2 | GPL-3 [expanded from: GPL (≥ 2)]
NeedsCompilation: yes
Materials: README NEWS
CRAN checks: SPAS results


Reference manual: SPAS.pdf
Vignettes: Automatic Pooling
Conne River 1991 Data
Conne River 1992 Data
Harrison River Female Chinook 2011 Data
Pooling Columns
Testing for Pooled Petersen
Things that can go wrong


Package source: SPAS_2024.1.31.tar.gz
Windows binaries: r-devel:, r-release:, r-oldrel:
macOS binaries: r-release (arm64): SPAS_2024.1.31.tgz, r-oldrel (arm64): SPAS_2024.1.31.tgz, r-release (x86_64): SPAS_2024.1.31.tgz, r-oldrel (x86_64): SPAS_2024.1.31.tgz
Old sources: SPAS archive

Reverse dependencies:

Reverse imports: Petersen


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