ncfile='sfc_pres_temp.nc'

%
% These are used to construct some example data. 
sample_pressure = 900;
sample_temp = 9.0;



%
% Create some pretend data. If this wasn't an example program, we
% would have some real data to write, for example, model
% output. 
lats = [25:0.5:27.5]';
NLAT = length(lats);
lons = [-125:0.5:-119.5]';
NLON = length(lons);

[Lon,Lat] = meshgrid([0:NLON-1],[0:NLAT-1]);
   
pres_out = sample_pressure + (Lon*NLAT+Lat);
temp_out = sample_temp + (Lon*NLON+Lat)/4;

%
% for the units attributes
PRES_UNITS='hPa';
TEMP_UNITS='celsius';
LAT_UNITS='degrees_north';
LON_UNITS='degrees_east';

%
% We will use mexnc to inquire about the number of variables, 
% dimensions, global attributes, etc.  We could use SNCTOOLS/nc_info
% to indirectly do many of the same things, though.
[ncid, status] = mexnc ( 'OPEN', ncfile, nc_nowrite_mode );
if status, error(mexnc('STRERROR',status)), end

% 
% There are a number of inquiry functions in netCDF which can be used
% to learn about an unknown netCDF file. NC_INQ tells how many netCDF
% variables, dimensions, and global attributes are in the file; also the
% dimension id of the unlimited dimension, if there is one.
[ndims_in, nvars_in, ngatts_in, unlimdimid_in, status] = mexnc ( 'INQ', ncid );
if status, error(mexnc('STRERROR',status)), end

%
% In this case we know that there are 2 netCDF dimensions, 4
% netCDF variables, no global attributes, and no unlimited
% dimension. */
if (ndims_in ~= 2 || nvars_in ~= 4 || ngatts_in ~= 0 || unlimdimid_in ~= -1) 
    error ( 'mexnc:inq did not return the right information!\n' );
end


status = mexnc ( 'CLOSE', ncid );
if status, error(mexnc('STRERROR',status)), end


%
% Read the coordinate variable data.
lats_in = nc_varget ( ncfile, 'latitude' );
lons_in = nc_varget ( ncfile, 'longitude' );

if any(lats_in - lats)
    error ( 'latitude did not match\n' );
end
if any(lons_in - lons)
    error ( 'longitude did not match\n' );
end

%
% Read the data. Since we know the contents of the file we know
% that the data arrays in this program are the correct size to
% hold all the data. 
pres_in = nc_varget ( ncfile, 'pressure' );
temp_in = nc_varget ( ncfile, 'temperature' );

%
% Check the data.
if any(pres_in - pres_out)
    error ( 'pressure did not match\n' );
end
if any(temp_in - temp_out)
    error ( 'temperature did not match\n' );
end

%
% Each of the netCDF variables has a "units" attribute. Let's read
% them and check them. 
lat_units_in = nc_attget ( ncfile, 'latitude', 'units' );
lon_units_in = nc_attget ( ncfile, 'longitude', 'units' );
pres_units_in = nc_attget ( ncfile, 'pressure', 'units' );
temp_units_in = nc_attget ( ncfile, 'temperature', 'units' );

if ~strcmp ( lat_units_in, LAT_UNITS )
    error ( 'latitude units did not match\n' );
end
if ~strcmp ( lon_units_in, LON_UNITS )
    error ( 'longitude units did not match\n' );
end
if ~strcmp ( temp_units_in, TEMP_UNITS )
    error ( 'temperature units did not match\n' );
end
if ~strcmp ( pres_units_in, PRES_UNITS )
    error ( 'pressure units did not match\n' );
end

fprintf(1, '*** SUCCESS reading example file sfc_pres_temp.nc!\n');