dsdata: Distance sampling workshop data

#' Golf tee data
#'
#' The data are from independent surveys by eight observers of a population of 250
#' groups (760 individuals) of golf tees.  The tees, of two colours, were placed 
#' in groups of between 1 and 8 in a survey region of 1680 m^2^, either exposed 
#' above the surrounding grass, or at least partially hidden by it.  They were 
#' surveyed by the 1999 statistics honours class at the Univ of St Andrews.
#' 
#' We treat each group of golf tees as a single animal with size equal to the 
#' number of tees in the group; yellow tees are male, green are female; tees 
#' exposed above the surrounding grass are classified as exposed, others as 
#' unexposed.  We are grateful to Miguel Bernal for making these data available; 
#' they were collected by him as part of a masters project.
#'
#' @name golftees
#' @aliases golftees_units
#' @docType data
#' @format The format is:
#' \describe{ List of 4 
#' $ book.tee.dataframe:'data.frame': 
#'   \item{$ object}{object ID}
#'   \item{$ observer}{observer ID}
#'   \item{$ detected}{detected or not detected}
#'   \item{$ distance}{perpendicular distance}
#'   \item{$ size}{group size}
#'   \item{$ sex}{number of tees in group}
#'   \item{$ exposure}{tee height above ground}  
#'   $ book.tee.region   :'data.frame': 2 obs. of 2 variables: ..
#'   \item{$ Region.Label}{stratum name}
#'   \item{$ Area}{stratum size}
#'   $ book.tee.samples   :'data.frame': 11 obs. of 3 variables: ..
#'   \item{$ Sample.Label}{transect label}
#'   \item{$ Region.Label}{stratum name}
#'   \item{$ Effort}{transect length}
#'   $ book.tee.obs :'data.frame': 162 obs. of 3 variables:
#'   \item{$ object}{object ID}
#'   \item{$ Region.Label}{stratum in which it was detected}
#'   \item{$ Sample.Label}{transect on which it was detected}
#'   }
#' @keywords datasets
#' @references 
#' Borchers, D. L., S.T. Buckland, and W. Zucchini. 2002. Estimating Animal Abundance: Closed Populations. Statistics for Biology and Health. London: Springer-Verlag. https://www.springer.com/gp/book/9781852335601.
#' 
#' Buckland, S.T., D.R. Anderson, K.P. Burnham, J.L. Laake, D.L. Borchers, and L. Thomas. Advanced Distance Sampling: Estimating Abundance of Biological Populations. OUP Oxford, 2004.
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