R/parse_swe_csv.R

In USGS-R/NWCCompare: Returns NWC comparison stats for two daily data sets

#' Function to return NWC Intercomparison portal modeled data for a given site
#'
#' This function accepts a url and returns a data frame of data for that SOS request
#'
#' @param input url for SOS service for desired site data
#' @return data frame containing desired time series with names 'date' and 'data'
#' @importFrom xml2 read_xml xml_find_first xml_text xml_ns
#' @importFrom readr read_delim
#' @export
#' @examples
#' parse_swe_csv(system.file('extdata','SWECSVBlock_daymet_example.xml',package='NWCCompare'))
parse_swe_csv <- function(input) {
  mod_open <- file(input,open="r")
  content<-paste(readLines(mod_open,warn=FALSE))
  close(mod_open,type="r")
  if (any(grepl('<ExceptionText>invalid parameter</ExceptionText>',content))) {
    stop('An invalid parameter error was encountered. The HUC may not exist.')
  }
  if (length(sapply(content,nchar))>1) {
    dat <- read_xml(input)
    
    dat <- read_delim(file = xml_text(xml_find_first(dat, 
                                                      "//swe:values", 
                                                      xml_ns(dat))), 
                       delim = ",", col_names = FALSE)
    
    names(dat) <- c('date', 'data')
    dat$date <- as.Date(dat$date)
    dat$data <- as.numeric(dat$data)
    dat <- as.data.frame(dat)
    attr(dat, "SRC") <- input
    class(dat) <- c("dat", "data.frame")
    return(dat)
  } else {
    dat<-""
    return(dat)}
}