netcdfwrite <- function(lon,lat,data,filename="data.nc",time=1,mv=-999) {

# Writes two-dimensional map or three-dimensional array of data, longitude vector,
# latitude vector and time vector into a netcdf file.
#
# Description:
#
#      Returns a netcdf file that contains a two-dimensional map or a 
#      three-dimensional array of data, a longitude vector, a latitude vector 
#      and a time vector
#
# Usage:
#
#      netcdfwrite(lon,lat,data,filename,time,mv)
#
# Arguments:
#
#   	 data:     two-dimensional map with first dimension longitude and
#                  second dimension latitude or three-dimensional array
#                  with first dimension longitude, second dimension latitude and
#                  third dimension time, containing the data to be written 
#                  to the netcdf file
#	 lon:	   a vector containing the longitudes of data
#        lat:      a vector containing the latitudes of data
#	 time:	   a vector containing the times of data in hours 
#                  since 1900-1-1 00:00:0.0 . Default is 1, which is
#                  appropriate for writing a two-dimensional map                  
#	 filename: string with the name of the netcdf file to be created.
#                  Default is "data.nc"
#        mv:       Value attributed to missing data. Default is -999
#
# Output:
#
#	 netcdf-file containing the data 
#
# Author:
#
#     Dag Johan Steinskog <dag.johan.steinskog@nersc.no>  5 January 2006
#     Caio Coelho <c.a.d.s.coelho@reading.ac.uk>
#
# Example:
#
#     x <- seq(-20, 20, 5)
#     y <- seq(30, 60, 5)
#     dims <- c(length(x), length(y), 100)
#     data <- array(rnorm(prod(dims)), dims)
#     time <- 1:100
#     # write a two-dimensional map of data to the netcdf file
#     netcdfwrite(x,y,data[,,3],filename="data.nc")
#     # write a three-dimensional array of data to the netcdf file
#     netcdfwrite(x,y,data,filename="data.nc",time)



if(length(time)==1){data<-array(data,c(dim(data)[1],dim(data)[2],1))}

#create netcdf file
#ncfile <- create.nc(filename,clobber)
ncfile <- create.nc(filename)


#give dimensions to variables
dim.def.nc(ncfile,"lon",length(lon))
dim.def.nc(ncfile,"lat",length(lat))
dim.def.nc(ncfile,"time",length(time))


# create variables
var.def.nc(ncfile,"lon","NC_FLOAT","lon")
var.def.nc(ncfile,"lat","NC_FLOAT","lat")
var.def.nc(ncfile,"time","NC_DOUBLE","time")
var.def.nc(ncfile,"data","NC_FLOAT",c("lon","lat","time"))
#var.def.nc(ncfile,"data","NC_DOUBLE",c("lon","lat"))


# add data to variables
var.put.nc(ncfile,"lat",lat)
var.put.nc(ncfile,"lon",lon)
var.put.nc(ncfile,"time",time)
var.put.nc(ncfile,"data",data)

# add description information to variables
att.put.nc(ncfile,"data","missing_value","NC_FLOAT",mv)

att.put.nc(ncfile,"lon","long_name","NC_FLOAT","Longitude")
att.put.nc(ncfile,"lon","units","NC_FLOAT","degrees_east")
att.put.nc(ncfile,"lon","axis","NC_FLOAT","X")

att.put.nc(ncfile,"lat","long_name","NC_FLOAT","Latitude")
att.put.nc(ncfile,"lat","units","NC_FLOAT","degrees_north")
att.put.nc(ncfile,"lat","axis","NC_FLOAT","Y")

att.put.nc(ncfile,"time","long_name","NC_DOUBLE","Time")
att.put.nc(ncfile,"time","units","NC_DOUBLE","hours since 1900-1-1 00:00:0.0")
att.put.nc(ncfile,"time","delta_t","NC_DOUBLE","0000-01-00 00:00:00")


# syncronize and close the netcdf file    
sync.nc(ncfile)
close.nc(ncfile)
}