% Purpose
%    gets spacial axis value from data file.
%
% Synopsis
%    axis_val = mexeps('getaxis',varcode,axid)
%    axis_val = mexeps('getaxis',varcode,axid, ax_range)
%
% Description
%    It returns value of spacial axis of a variable from the data file. 
%    The variable is refered to by variable code, varcode. The axis is
%    refered to by a number, axid: 1 for x-axis; 2 for y-axis; and 3 
%    for z-axis. The ax_range is optional. If ax_range is not specified,
%    all values will be returned; otherwise, ax_range is a 1x2 array
%    contains [lower upper] limits of the axis you want to get.
%
% Examples
%    Open a data file and get x, y, z value of first variable.
%
%      currentfile = mexeps('openr','datafile.cdf');
%      var_list = mexeps('varlist');
%      varcode = var_list(1); 
%      x = mexeps('getaxis',varcode,1);
%      y = mexeps('getaxis',varcode,2);
%      z = mexeps('getaxis',varcode,3);
%      ...
%
% See Also
%    gettaxis
%