Fixed slight typo in help file.

R/getParameterInfo.r

@@ -3,7 +3,7 @@
 #' 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 vector USGS parameter code.  This is usually an 5 digit number.
+#' @param parameterCd vector of USGS parameter codes.  This is usually an 5 digit number.
 #' @param interactive logical Option for interactive mode.  If true, there is user interaction for error handling and data checks.
 #' @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)