smwrQW: Tools for censored data analysis

#' Atrazine Data

#' A dataset of atrazine samples, replicates, and blanks collected by the U.S.
#'Geological Survey from October 1, 2001 through September 30, 2012.
#'
#' @details The sample medium codes are regular water-quality sample, WS; replicate
#'water-quality sample, WSQ; and field blank, OAQ. The sample type codes are regular 
#'sample with no QAQC sample, 9; regular sample with QAQC or the replicate sample, 7;
#'and field blank , 2.
#'
#' @name atrazine.df
#' @docType data
#' @usage atrazine.df
#' @format Data frame with 13106 rows and 12 columns\cr
#'\tabular{lll}{
#'Name \tab Type \tab Description\cr
#'staid \tab character \tab USGS station number\cr
#'Date \tab Date \tab Sample date\cr
#'MEDIUM_CD \tab character \tab Sample medium code, see \bold{Details}\cr
#'SAMP_TYPE_CD \tab integer \tab Sample type code, see \bold{Details}\cr
#'sched \tab character \tab Lab schedule\cr
#'RESULT_VA \tab numeric \tab Numeric value of the concentration\cr
#'REMARK_CD \tab character \tab Remark code for the value\cr
#'RPT_LEV_VA \tab numeric \tab Reporting level\cr
#'RPT_LEV_CD \tab character \tab Reporting level code\cr
#'Units \tab character \tab Units of the concentration\cr
#'QW_METHOD_CD \tab character \tab Lab method code\cr
#'PARAMETER_CD \tab character \tab Parameter code\cr
#'}
#' @source Data retreived from the national water information system and processed 
#'by Jeffery Martin and Laura Medalie of the U.S. Geological Survey.
#' @keywords datasets
#' @examples
#' data(atrazine.df)
#' # How many different kinds of samples?
#' with(atrazine.df, table(MEDIUM_CD))
#' # Now many stations?
#' with(atrazine.df, table(staid))
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