ForestPlotR: Tree growth as a function of its neighbors

#' Repeated size measurements and mortality records for 9155 trees.
#' 
#' A dataset containing repeated size measurements and mortality records for
#' 9155 trees in 15 mapped forest stands located in Mount Rainier National Park,
#' WA, USA. These stands are part of the Pacific Northwest Permanent Sample Plot
#' Network (\url{http://pnwpsp.forestry.oregonstate.edu/}). Each row represents
#' a single measurement of a single tree and a determination of whether it was
#' alive or dead. PLEASE NOTE: the mortality data in the \code{mort} column were
#' randomly generated for the purposes of demonstrating functions in this
#' package and should not be used for real analysis. Although mortality data
#' are collected in these stands, mortality rates are extremely low and
#' therefore the real mortality data could not be used for demonstrating the
#' mortality model function in this package 
#' 
#' @format A data frame with 60114 rows and 7 variables:
#' \describe{
#'   \item{tree_id}{unique identification code of the tree}
#'   \item{stand_id}{name of stand in which tree is located}
#'   \item{tag}{unique tag number of the tree}
#'   \item{species}{species identity of tree as a four letter code}
#'   \item{year}{year when measurement was taken}
#'   \item{dbh}{diameter at breast height of the tree at the time of
#'   measurement, in cm}
#'   \item{mort}{tree mortality status with 1 meaning dead and 0 meaning alive}
#' }
#' @source Data are available from the Pacific Northwest Permanent Sample Plot
#' Network on request \url{http://pnwpsp.forestry.oregonstate.edu/data}
"tree"