SOM Toolbox Online documentation




 Forms a map unit patch for SOM_CPLANE function. Mainly a subroutine
 of SOM_CPLANE, although can be used for on its own as well.

Required input arguments

 lattice (string)

    'hexa'  produces vertex coordiantes for a hexagoanl patch which 
            has its center on (0,0), unit width, and a height of
            1.3334 units. This is not a regular hexagon but such that
            the node which has topological coordinates (a,b) has its
            center in the visualization at coordinates (a,b) for odd
            a and at (a,b+.5) for even a. The non-regular look of the
            patch is taken care simply by changing the axis ratio.

    'rect'  produces vertex coordinates for a uniform rectangular patch.
            having its center on (0,0) and unit sidelength. Used as a
            subfunction in SOM_CPLANE.

    'hexagon' produces vertex coordinates for a regular hexagonal patch.
            It may be used in som_cplane if, for some reason, truly
            regular hexagons are needed instead of the default unit
            markers which are not uniform, but have integer
            y-coordinates in the lattice.

Output arguments

 p (matrix) The 2-dimensional vertex coordinates: 

   case 'rect'        case 'hexa'                case 'hexagon'
    p=[[-.5 -.5];...     p=[[0     0.6667];...    p=[[0     0.5774];...
       [-.5  .5];...        [0.5   0.3333];...       [0.5   0.2887];...
       [ .5  .5];...        [0.5  -0.3333];...       [0.5  -0.2887];...
       [ .5 -.5]];          [0    -0.6667];...       [0    -0.5774];...
                            [-0.5 -0.3333];...       [-0.5 -0.2887];...
                            [-0.5  0.3333]];         [-0.5  0.2887]]; 


  som_cplane(vis_patch('rect'),[6 5],'none');
  % this produces the same result as som_cplane('rect',[6 5], 'none') 

  som_cplane(vis_patch('hexa'), vis_unit_coord('hexa',[6 5]), 'none');
  % produces in principle the same result as 
  % som_cplane(vis_patch('hexa'),[6 5],'none'), 
  % _but_ in this case the axis are not rescaled and the non-regular 
  % shape of hexagons can be seen.

  som_cplane(vis_patch('hexagon'), som_unit_coords([6 5],'hexa'), 'none');
  % produces a truly regular hexa lattice 

See also

vis_unit_coord The default 'hexa' and 'rect' coordinates in visualizations
som_unit_coords Locations of units on the SOM grid.