trtools: Miscellaneous Tools for Teaching Statistics

#' Truncated counts of gallfly eggs and gall-cells.
#'
#' Data from a study that investigated the number of eggs and gall-cells from gall flies (Urophora jaceana) during two seasons in the flower heads of knapweed (Centaurea nemoralis). 
#'
#' @format A data frame 1411 observations and three variables:
#' \describe{
#'    \item{y:}{number of eggs or gall-cells}
#'    \item{year:}{year of observations (1935 or 1936)}
#'    \item{stage:}{developmental stage observed (egg or gall)}
#' }
#'
#' @note These data were used by Finney and Varley (1955) as an example for modeling using a truncated Poisson distribution. For reasons that are not entirely clear, no flower heads with zero eggs or gall-cells were reported. The original source of the data is Varley (1947). 
#'
#' @source Finney, D. J. & Varley, G. C. (1955). An example of the truncated Poisson distribution. \emph{Biometrics}, \emph{11}, 387-394.
#' 
#' Varley, G. C. (1947). The natural control of population balance in the knapweed gall-fly (Erophora jaceana). \emph{Journal of Animal Ecology}, \emph{16}, 139-187. 
#' 
"gallfly"