netcdfread<-function(file,lonname='longitude',latname='latitude',timename='time',dataname,unpack=F) {

#
# Extract longitude vector, latitude vector, time vector and 
# data array from a netcdf file.
#
# Description:
#
#      Returns a vector of longitudes, a vector of latitudes, a vector of times
#      and an array of data from a netcdf file.
#
# Usage:
#
#      netcdfread(file,lonname,latname,timename,dataname,unpack=F)
#
# Arguments:
#
#   file:     String containing the full path and netcdf file name
#
#   lonname:  String containing the name of the longitude variable. 
#             Default name is "longitude".
#
#   latname:  String containing the name of the latitude variable
#             Default name is "latitude".
#
#   timename: String containing the name of the time variable.
#	      Default name is "time"
#
#   dataname: String containing the name of the data variable
#
#   unpack:   Logical. If TRUE unpacks data contained in variable
#             dataname by performing the following transformation:
#             unpacked_data_value=packed_data_value*scale_factor+add_offset,
#             where, scale_factor and add_offset are constant netcdf attributes
#             of variable dataname. Default is FALSE.
#
# Output:
#
#   $lonncfile:  Vector of longitudes
#   $latncfile:  Vector of latitudes
#   $timencfile: Vector of times
#   $datancfile: Array of data
#
# Author:
#
#      Chris Ferro <c.a.t.ferro@reading.ac.uk> 9 June 2005
#      Dag Johan Steinskog <dag.johan.steinskog@nersc.no> 
#      Caio Coelho <c.a.d.s.coelho@reading.ac.uk> 
#
# Examples:
#
#      # First run the line below to extract the data structure/information
#      # so that you are able to know the names of variables 
#      netcdfinfo("netcdf_file_name.nc")
#
#      netcdfread("netcdf_file_name.nc","lon_name","lat_name","time_name","data_name")
#      netcdfread("/home/username/netcdf_file_name.nc","lon_name","lat_name","time_name","data_name")
#
#      Note: The user should use a netcdf file to be able to run these examples


 
# open a netcdf file
ncfile <- open.nc(file)

# get latitude and longitude
lonncfileaux <- var.get.nc(ncfile, lonname)
latncfileaux <- var.get.nc(ncfile, latname)

# get data and time
datancfile <- var.get.nc(ncfile, dataname)
timencfile <- var.get.nc(ncfile, timename)

if(unpack){
datancfile<-datancfile*att.get.nc(ncfile,dataname,"scale_factor")+att.get.nc(ncfile,dataname,"add_offset")
}

# sort latitude and longitude in ascending order
lonncfile <- sort(lonncfileaux)
latncfile <- sort(latncfileaux)

# rearange data 
datancfile<-datancfile[order(lonncfileaux),order(latncfileaux),]

invisible(list(lonncfile=lonncfile,latncfile=latncfile,timencfile=timencfile,datancfile=datancfile))

}