% Purpose
%    writes out a hyperslab of a variable to data file
%
% Synopsis
%    mexeps('putvar',varcode,var,var_shape)
%    mexeps('putvar',varcode,var,var_shape,var_range)
%
% Description
%    It writes out a hyperslab of a variable to netCDF data file. 
%    The variable is refered be by variable code, varcode.  The 
%    input argument var is variable value; var_shape is the 
%    variable shape; and var_range is optional.  When var_range 
%    is not specified, all variable values will be written out; 
%    when var_range is specified, it is a 4x2 matrix with 
%    [lower upper] limits of x, y, z, and t axis of the variable 
%    you want to write. The type of variable written to the netCDF 
%    file is float.
%
% Examples
%    Open a pointer file, then open a netCDF data file and write
%    variable to data file.
%
%      mexeps('openw','pointer.file');       % open pointer file
%      mexeps('setnextw','datafile.cdf');    % open data file
%
%      ...     % writes out axis, attributes, etc.
%
%      var_shape = [1 1 5 1];
%      varcode = 20;
%      temp = [16; 15.8; 15.6; 15.4; 15.5];
%      ax_range = [[1 1];[1 1];[2 4];[1 1]];
%      mexeps('putvar',20,temp,ax_range);    %writes out temp(2:4)
% 
% See Also
%    setvar, putaxis, puttaxis
%