function distance( path)
% distance( centers, xave, yave, path )
% 
% centers : an image of the tile centers, oriented vertically
% xave, yave : the average distance between adjacent centers
% path : the file path to save connection data to
% 
% finds connections between tiles, assuming that the crystal is oriented
% vertically. Then allows user to adjust found connections if that option
% is chosen
% method: look in range of anticipated connection 

global OPTIONS;

load('-mat', path, 'x','y','N','xave','yave', 'rotim');

figure(2)
    imagesc(rotim)
    colormap gray
    hold on
    plot(x,y,'g.')

yshift = floor(yave);
xshift = floor(xave);
yrange = floor(2*yave/5);
xrange = floor(2*xave/5);
% stores connections
    % stores index of points and its 6 connections in a row
    % 1 2 6 should be larger than the row number
    % 3 4 5 should be smaller than the row number.
    % all connections stored twice, for convenience
conn = zeros(N, 6);
for n = 1:N
    
    % find points horizontal to the right ---------------------------------
    % lookhere is the center of where to look for tile centers
    lookhere(1) = x(n) + xshift;
    lookhere(2) = y(n);
    t = find( x < (lookhere(1) + xrange) & x > (lookhere(1) - xrange) );
    t2 = find( y(t(:)) < (lookhere(2) + yrange) & y(t(:)) > (lookhere(2) - yrange), 1, 'last');
    
    if ( ~isempty(t2) )
        %horizontal and to the right connections
        hr = t(t2);
        conn(n, 1) = hr;
        conn(hr, 4) = n;
        plot( [x(n),x(hr)],[y(n), y(hr)],'y-' )
    end
    t = [];
    t2 = [];
    
    % find points to the lower right --------------------------------------
    lookhere(1) = x(n) + xshift/2;
    lookhere(2) = y(n) + yshift;
    t = find( x < (lookhere(1) + xrange) & x > (lookhere(1) - xrange) );
    t2 = find( y(t(:)) < (lookhere(2) + yrange) & y(t(:)) > (lookhere(2) - yrange), 1, 'last');
   
    if ( ~isempty(t2) )
        % down and to the right connections
        lr = t(t2);
        conn(n, 2) = lr;
        conn(lr, 5) = n;
        plot( [x(n),x(lr)],[y(n), y(lr)],'m-' )
    end
    t = [];
    t2 = [];
    
    % find points to the lower left ---------------------------------------
    lookhere(1) = x(n) - xshift/2;
    lookhere(2) = y(n) + yshift;
    t = find( x < (lookhere(1) + xrange) & x > (lookhere(1) - xrange) );
    t2 = find( y(t(:)) < (lookhere(2) + yrange) & y(t(:)) > (lookhere(2) - yrange), 1, 'last');
   
    if ( ~isempty(t2) )
        %horizontal and to the right connections
        ll = t(t2);
        conn(n, 3) = ll;
        conn(ll, 6) = n;
        plot( [x(n),x(ll)],[y(n), y(ll)],'c-' )
    end
    t = [];
    t2 = [];
    
end

% fill in isolated missing connections
conn = fillinconn(conn,N,x,y, true);

hold off
  
% saves variable 'conn' to desired location
save( path, 'conn', '-mat', '-append');

if ( ~isempty(find(OPTIONS == 8)) )  
    modify_conn(path);
end