#' A list of statistic codes can be found here: \url{http://help.waterdata.usgs.gov/code/stat_code_query?fmt=html}
#' A list of statistic codes can be found here: \url{http://help.waterdata.usgs.gov/code/stat_code_query?fmt=html}
#'
#'
#' @param siteNumber string USGS site number. This is usually an 8 digit number
#' @param siteNumber string USGS site number. This is usually an 8 digit number
#' @param ParameterCd string or vector of USGS parameter code. This is usually an 5 digit number..
#' @param parameterCd string or vector of USGS parameter code. This is usually an 5 digit number..
#' @param StartDate string starting date for data retrieval in the form YYYY-MM-DD.
#' @param startDate string starting date for data retrieval in the form YYYY-MM-DD.
#' @param EndDate string ending date for data retrieval in the form YYYY-MM-DD.
#' @param endDate string ending date for data retrieval in the form YYYY-MM-DD.
#' @param StatCd string USGS statistic code. This is usually 5 digits. Daily mean (00003) is the default.
#' @param statCd string USGS statistic code. This is usually 5 digits. Daily mean (00003) is the default.
#' @param format string, can be 'tsv' or 'xml', and is only applicable for daily and unit value requests. 'tsv' returns results faster, but there is a possiblitiy that an incomplete file is returned without warning. XML is slower,
#' @param format string, can be 'tsv' or 'xml', and is only applicable for daily and unit value requests. 'tsv' returns results faster, but there is a possiblitiy that an incomplete file is returned without warning. XML is slower,
#' but will offer a warning if the file was incomplete (for example, if there was a momentary problem with the internet connection). It is possible to safely use the 'tsv' option,
#' but will offer a warning if the file was incomplete (for example, if there was a momentary problem with the internet connection). It is possible to safely use the 'tsv' option,
#' but the user must carefully check the results to see if the data returns matches what is expected. The default is 'tsv'.
#' but the user must carefully check the results to see if the data returns matches what is expected. The default is 'tsv'.