function [DEM, DEM_nan, COLS, ROWS, xllcorner,.. 
yllcorner, cellsize, nodata] = read_dem(filename, dlm)
% read_dem(filename, dlm) outputs a DEM and a DEM with NaN values from an
% ASCII file exported from ArcGIS
%       filename = 'filename.txt'
%       dlm = 'delimiter', ' ' = space (default if none set), '\t' = tab

% Test case
% filename = 'fake_dem.txt';      % Enter in the file to be read

if nargin < 2, dlm = ['']; end

% Format of text files
% % % % % % % % % % % % % % % % % % % % % % % % % % % % % 
% ncols         m
% nrows         n
% xllcorner     502035
% yllcorner     6622425
% cellsize      30
% NODATA_value  -9999
% row 1 col1 [space] col2 [space]... colm [space-return]
% row 2 data [space-return]
% ...
% ...
% ...
% row n data [space-return]
% % % % % % % % % % % % % % % % % % % % % % % % % % % % % 

% Find the text values
fid = fopen(filename);      
header = textscan(fid, '%s %f');
fclose(fid);
% header{1} are the text labels
% header{2} are the values - reassigned to their own variables below
% Clear everything but the real header values
header{1}(7:end) = [];
header{2}(7:end) = [];

% Set variables
COLS = header{2}(1);
ROWS = header{2}(2);
xllcorner = header{2}(3);
yllcorner = header{2}(4);
cellsize = header{2}(5);
nodata = header{2}(6);

DEM = dlmread(filename, dlm, 6, 0);
% This adds a row of zeros at the end now, so I need to fix that
% Not so elegant fix
if length(DEM(1,:)) > ROWS
    DEM(:, end) = [];
end

% For easy plotting in matlab
% Need to flipud because of how ARC exports
DEM = flipud(DEM);

% Make a version with NaN
DEM_nan = DEM;
DEM_nan(DEM == nodata) = NaN;

% Rachel Headley - 6 April 2007
% write_dem does the reverse of this