R/pointGFS.R

In meteoForecast: Numerical Weather Predictions

pointGFS <- function(lon, lat, vars,
                     day=Sys.Date(), run='00',
                     resolution = NULL, ...)
{

    completeURL <- composeURL(vars, day, run,
                              c(lon, lat), '&temporal=all',
                              resolution = resolution,
                              service = 'gfs',
                              point=TRUE, ...)
    ## Check if point is inside bounding box
    extGFS <- mfExtent("gfs")
    if (!isInside(lon, lat, extGFS))
        stop('Point outside GFS-MG region.')

    tmpfile <- tempfile(fileext='.csv')
    success <- try(suppressWarnings(
        download.file(completeURL,
                      tmpfile, quiet=TRUE)),
        silent=TRUE)

    if (inherits(success, "try-error"))
        stop('Data not found. Check the date and variables name.\nURL: ',
             completeURL)
    else
    {
        z <- read.csv(tmpfile)
        vert <- any(grepl('vertCoord', names(z)))
        idx <- as.POSIXct(z[,1], format='%Y-%m-%dT%H:%M:%SZ', tz = 'UTC')
        lat <- as.numeric(as.character(z[1, 2]))
        lon <- as.numeric(as.character(z[1, 3]))
        if (vert)
            vertCoord <- as.numeric(as.character(z[1, 4]))

        ## Subset the columns with variables (time index, lat, long, and
        ## vertical coordinate are not needed)
        nc <- ncol(z)
        nv <- length(vars)
        z <- zoo(z[, (nc - nv + 1):nc], idx)
        names(z) <- vars

        attr(z, 'lat') <- lat
        attr(z, 'lon') <- lon
        if (vert) attr(z, 'vertCoord') <- vertCoord
        
        message('File available at ', tmpfile)
        message('URL: ', completeURL)

        z

    }

}