wolffd@0: function p=vis_patch(lattice)
wolffd@0: 
wolffd@0: % VIS_PATCH Defines the basic patches (hexa and rect) used in SOM_CPLANE
wolffd@0: %
wolffd@0: %  p = vis_patch(lattice)
wolffd@0: %
wolffd@0: %  Input and output arguments: 
wolffd@0: %   lattice   (string) 'rect', 'hexa' or 'hexagon'
wolffd@0: %
wolffd@0: %   p         (matrix) size Lx2, defines the vertices of the patch
wolffd@0: %
wolffd@0: % This function produces vertex coordinates for a patch presenting
wolffd@0: % a map unit in hexagonal or rectangular lattice with its centre in (0,0). 
wolffd@0: %
wolffd@0: % For more help, try 'type vis_patch' or check out online documentation.
wolffd@0: % See also SOM_CPLANE, PATCH.
wolffd@0: 
wolffd@0: %%%% DETAILED DESCRIPTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
wolffd@0: %
wolffd@0: % vis_patch
wolffd@0: %
wolffd@0: % SYNTAX
wolffd@0: %  
wolffd@0: %  p = vis_patch(lattice)
wolffd@0: % 
wolffd@0: % DESCRIPTION
wolffd@0: % 
wolffd@0: % Forms a map unit patch for SOM_CPLANE function. Mainly a subroutine
wolffd@0: % of SOM_CPLANE, although can be used for on its own as well.
wolffd@0: %
wolffd@0: % REQUIRED INPUT ARGUMENTS
wolffd@0: %
wolffd@0: % lattice (string)
wolffd@0: % 
wolffd@0: %    'hexa'  produces vertex coordiantes for a hexagoanl patch which 
wolffd@0: %            has its center on (0,0), unit width, and a height of
wolffd@0: %            1.3334 units. This is not a regular hexagon but such that
wolffd@0: %            the node which has topological coordinates (a,b) has its
wolffd@0: %            center in the visualization at coordinates (a,b) for odd
wolffd@0: %            a and at (a,b+.5) for even a. The non-regular look of the
wolffd@0: %            patch is taken care simply by changing the axis ratio.
wolffd@0: %
wolffd@0: %    'rect'  produces vertex coordinates for a uniform rectangular patch.
wolffd@0: %            having its center on (0,0) and unit sidelength. Used as a
wolffd@0: %            subfunction in SOM_CPLANE.
wolffd@0: %
wolffd@0: %    'hexagon' produces vertex coordinates for a regular hexagonal patch.
wolffd@0: %            It may be used in som_cplane if, for some reason, truly
wolffd@0: %            regular hexagons are needed instead of the default unit
wolffd@0: %            markers which are not uniform, but have integer
wolffd@0: %            y-coordinates in the lattice.
wolffd@0: %
wolffd@0: % OUTPUT ARGUMENTS
wolffd@0: %
wolffd@0: % p (matrix) The 2-dimensional vertex coordinates: 
wolffd@0: %
wolffd@0: %   case 'rect'        case 'hexa'                case 'hexagon'
wolffd@0: %    p=[[-.5 -.5];...     p=[[0     0.6667];...    p=[[0     0.5774];...
wolffd@0: %       [-.5  .5];...        [0.5   0.3333];...       [0.5   0.2887];...
wolffd@0: %       [ .5  .5];...        [0.5  -0.3333];...       [0.5  -0.2887];...
wolffd@0: %       [ .5 -.5]];          [0    -0.6667];...       [0    -0.5774];...
wolffd@0: %                            [-0.5 -0.3333];...       [-0.5 -0.2887];...
wolffd@0: %                            [-0.5  0.3333]];         [-0.5  0.2887]]; 
wolffd@0: %
wolffd@0: % EXAMPLES
wolffd@0: %
wolffd@0: %  som_cplane(vis_patch('rect'),[6 5],'none');
wolffd@0: %  % this produces the same result as som_cplane('rect',[6 5], 'none') 
wolffd@0: %  
wolffd@0: %  som_cplane(vis_patch('hexa'), vis_unit_coord('hexa',[6 5]), 'none');
wolffd@0: %  % produces in principle the same result as 
wolffd@0: %  % som_cplane(vis_patch('hexa'),[6 5],'none'), 
wolffd@0: %  % _but_ in this case the axis are not rescaled and the non-regular 
wolffd@0: %  % shape of hexagons can be seen.
wolffd@0: %
wolffd@0: %  som_cplane(vis_patch('hexagon'), som_unit_coords([6 5],'hexa'), 'none');
wolffd@0: %  % produces a truly regular hexa lattice 
wolffd@0: %
wolffd@0: % SEE ALSO 
wolffd@0: %
wolffd@0: %  vis_unit_coord   The default 'hexa' and 'rect' coordinates in visualizations
wolffd@0: %  som_unit_coords  Locations of units on the SOM grid.
wolffd@0: 
wolffd@0: % Copyright (c) 1999-2000 by the SOM toolbox programming team.
wolffd@0: % http://www.cis.hut.fi/projects/somtoolbox/             
wolffd@0: 
wolffd@0: % Version 2.0beta Johan 041099
wolffd@0: 
wolffd@0: if ~ischar(lattice)
wolffd@0:   error('Input argument should be a string')
wolffd@0: else
wolffd@0:   switch lattice
wolffd@0:   case 'rect'
wolffd@0:     p=[[-.5 -.5]; ...
wolffd@0:       [-.5 .5];...
wolffd@0:       [.5 .5];...
wolffd@0:       [.5 -.5]];
wolffd@0:   case 'hexagon'
wolffd@0:     p=[[0 0.5774];...
wolffd@0:       [0.5 0.2887];...
wolffd@0:       [0.5 -0.2887];...
wolffd@0:       [0 -0.5774];...
wolffd@0:       [-0.5 -0.2887];...
wolffd@0:       [-0.5 0.2887]];
wolffd@0:   case 'hexa'
wolffd@0:     p=[[0 0.6667];...
wolffd@0:       [0.5 0.3333];...
wolffd@0:       [0.5 -0.3333];...
wolffd@0:       [0 -0.6667];...
wolffd@0:       [-0.5 -0.3333];...
wolffd@0:       [-0.5 0.3333]];
wolffd@0:   otherwise
wolffd@0:     error('Unknown lattice');
wolffd@0:   end
wolffd@0: end
wolffd@0: 
wolffd@0: