readNWISpCode.r

#' USGS Parameter Data Retrieval
#'
#' Imports data from NWIS about meaured parameter based on user-supplied parameter code.
#' This function gets the data from here: \url{http://nwis.waterdata.usgs.gov/nwis/pmcodes}
#'
#' @param parameterCd character of USGS parameter codes.  This is usually an 5 digit number.
#' @keywords data import USGS web service
#' @return parameterData dataframe with all information from the USGS about the particular parameter (usually code, name, short name, units, and CAS registry numbers)
#' @export
#' @examples
#' # These examples require an internet connection to run
#' paramINFO <- readNWISpCode(c('01075','00060','00931'))
readNWISpCode <- function(parameterCd){
 
  pcodeCheck <- all(nchar(parameterCd) == 5) & all(!is.na(suppressWarnings(as.numeric(parameterCd))))
  
  if(!pcodeCheck){
    goodIndex <- which(parameterCd %in% parameterCdFile$parameter_cd)
    if(length(goodIndex) > 0){
      badPcode <- parameterCd[-goodIndex]
    } else {
      badPcode <- parameterCd
    }
    message("The following pCodes seem mistyped:",paste(badPcode,collapse=","))
    parameterCd <- parameterCd[goodIndex]
  }
  
  parameterCdFile <- parameterCdFile
  
  parameterData <- parameterCdFile[parameterCdFile$parameter_cd %in% parameterCd,]

  if(nrow(parameterData) != length(parameterCd)){
    
    if(length(parameterCd) == 1){
      url <- paste0("http://nwis.waterdata.usgs.gov/nwis/pmcodes/pmcodes?radio_pm_search=pm_search",
                   "&pm_search=", parameterCd,
                   "&format=rdb", "&show=parameter_group_nm",
                   "&show=parameter_nm", "&show=casrn",
                   "&show=srsname", "&show=parameter_units")
      newData <- importRDB1(url,asDateTime = FALSE)
    } else {
      
      #TODO: add else...
      fullURL <- "http://nwis.waterdata.usgs.gov/nwis/pmcodes/pmcodes?radio_pm_search=param_group&pm_group=All+--+include+all+parameter+groups&format=rdb&show=parameter_group_nm&show=parameter_nm&show=casrn&show=srsname&show=parameter_units"
      fullPcodeDownload <- importRDB1(fullURL)
      newData <- fullPcodeDownload[fullPcodeDownload$parameter_cd %in% parameterCd,]
      
    }
    return(newData)
    
  } else {
    return(parameterData)
  }
  
  
}