centers                 Coordinates of 9 sites considered as potential
                        centers of origin of the Neolithic expansion.
                        Modified from Pinhasi et al. (2005).
filterDates             Filter archaeological site coordinates and
                        dates, retaining only the earliest radiocarbon
                        date per site.
interpolateIDW          Interpolate using inverse distance weighting.
iterateSites            Perform regression of dates versus distances
                        from multiple potential origins in order to
                        find the best model. It is also possible to
                        specify multiple distances for the spatial
                        binning of the dates.
land                    Land polygons.
modelDates              Perform regression of archaeological dates on
                        great circle distances from a hypothetical
                        origin. Dates can be filtered to retain only
                        the earliest dates per distance bins (Hamilton
                        and Buchanan 2007). Bootstrap is executed to
                        account for uncertainty in calibrated dates.
                        Regression can be either reduced major axis or
                        ordinary least squares. If using ordinary least
                        squares, regression is performed both on
                        time-versus-distance and on
                        distance-versus-time.
neof                    Radiocarbon dates and coordinates of 717
                        Neolithic sites in the Near East and Europe.
                        Modified from Pinhasi et al. (2005). Only the
                        earliest dates per site are included.
plot.dateMap            Plot a map with the results of the iteration
                        over multiple sites, showing an interpolated
                        surface of r values for the sites considered as
                        potential origins.
plot.dateModel          Plot the results of the regression bootstrap on
                        archaeological dates versus distances from a
                        hypothetical origin, with fitted lines.
sampleCalDates          Extract a single year estimate for ranges of
                        calibrated dates with a probability given by
                        the calibrated probability distribution.
summary.dateModel       Return summary statistics for a dateModel
                        object.
