New CRAN release of mrds and Distance packages

Posted 04 January 2024 by Laura Marshall

We announce the release of mrds 2.3.0 and Distance 1.0.9 on CRAN. An important update is that the default encounter rate variance estimator for point transect surveys has now been changed from the ‘P3’ estimator to the ‘P2’ estimator. Please follow link for further details.

This change will only make a difference to the variance estimate when there is variable survey effort (e.g. variable numbers of visits) between points, which is rare in practice. In the case that points are visited the same number of times these two estimators (‘P2’ and ‘P3’) are equivalent and there will be no difference in the variance estimates.

This change to the default encounter rate estimator was made for consistency with the line transect estimator, where the equivalent ‘R2’ estimator is the default, and also with Distance for Windows where ‘R2’ and ‘P2’ are the defaults for line and point transect surveys, respectively. ‘R2’ and ‘P2’ are both design-based variance estimators, while ‘R3’ and ‘P3’ are model-derived; the design-based line transect estimator was found to be superior when model assumptions fail (see Fewster et. al. 2009, for details).

These releases also address a number of reported issues within the packages. A full list of changes and updates is given below.

Thanks to those who have made feature requests or reported issues. If you do find any problems, or want to suggest a new feature, please feel free to raise an issue at or in the github page for each package

Full list of changes and updates:


Changes in version 2.3.0 (submitted to on CRAN 18/12/2023)


Changes in version 1.0.9 (accepted to CRAN 21/12/2023)