R/DS.GCM.to.grid.R

In jjvanderwal/climates: Methods for working with weather & climate

#' @title Downscale Global GCM Models to a Regular Grid
#' 
#' @description need a function to downscale data to regular grid
#' 
#' @details nc should be from extend.global.data
#' 
#' @aliases DS.GCM.to.grid DS.GCM.to.pnt
#' @param nc
#' @param cellsize
#' @param type
#' @param lon
#' @param lat
#' @return Downscale Global GCM Models to a Regular Grid
#' @author Jeremy VanDerWal \email{jjvanderwal@@gmail.com}
#' @export
#' @examples
#' \dontrun{
#' ##---- Should be DIRECTLY executable !! ----
#' ##-- ==>  Define data, use random,
#' ##--	or do  help(data=index)  for the standard data sets.
#' 
#' ## The function is currently defined as
#' function(nc,cellsize=0.2,type=2) {
#' 	#ensure nc is from retrieve.nc or similar
#' 	if (all(c('dat','tim','lat', 'lon') %in% names(nc))==FALSE) 
#'   stop('nc must have objects named dat, lat, lon and tim as from 
#'   retrieve.nc of clim.pact package, append.nc or extract.monthly.averages')
#' 	if (!(type %in% 1:3)) stop('type must be 1,2 or 3... see help file')
#' 	#do the work
#' 	lat = seq(-90+0.5*cellsize,90-0.5*cellsize,cellsize)
#' 	lon = seq(-180+05*cellsize,180-0.5*cellsize,cellsize)
#' 	out = array(0,dim=c(length(nc$tim),length(lat),length(lon)))
#' 	for (ii in 1:length(nc$tim)) { out[ii,,] = 
#'   interp2grid(nc$dat[ii,,],lon,lat,nc$lon,nc$lat,type=type) }
#' 	return(list(dat=out,lon=lon,lat=lat,tim=nc$tim))
#'   }
#' }
#' 
DS.GCM.to.grid = function(nc,lon=c(-180,180),lat=c(-90,90),cellsize=0.2,type=2) {
	#ensure nc is from retrieve.nc or similar
	if (all(c('dat','tim','lat', 'lon') %in% names(nc))==FALSE) stop('nc must have objects named dat, lat, lon and tim as from retrieve.nc of clim.pact package, append.nc or extract.monthly.averages')
	if (!(type %in% 1:3)) stop('type must be 1,2 or 3... see help file')
	#do the work
	lat = seq(lat[1]+0.5*cellsize,lat[2]-0.5*cellsize,cellsize)
	lon = seq(lon[1]+0.5*cellsize,lon[2]-0.5*cellsize,cellsize)
	out = array(0,dim=c(length(nc$tim),length(lat),length(lon)))
	for (ii in 1:length(nc$tim)) { cat('tim -',ii,'\n'); out[ii,,] = interp2grid(nc$dat[ii,,],lon,lat,nc$lon,nc$lat,type=type); gc(verbose=FALSE) }
	out = list(dat=out,lon=lon,lat=lat,tim=nc$tim)
	class(out) = unique(c(class(out),'nc'))
	return(out)
}

DS.GCM.to.pnt = function(nc,lon,lat,type=2) {
	#ensure nc is from retrieve.nc or similar
	if (all(c('dat','tim','lat', 'lon') %in% names(nc))==FALSE) stop('nc must have objects named dat, lat, lon and tim as from retrieve.nc of clim.pact package, append.nc or extract.monthly.averages')
	if (!(type %in% 1:3)) stop('type must be 1,2 or 3... see help file')
	#do the work
	out = data.frame(lon=lon,lat=lat)
	for (ii in 1:length(nc$tim)) { out[paste('tim.',nc$tim[ii],sep='')] = interp2pnt(nc$dat[ii,,],lon,lat,nc$lon,nc$lat,type=type); gc(verbose=FALSE) }
	return(out)
}