Number the grid points in a two dimensional region.
G = NUMGRID('R',n) numbers the points on an n-by-n grid in
the subregion of -1<=x<=1 and -1<=y<=1 determined by 'R'.
SPY (NUMGRID('R',n)) plots the points.
DELSQ (NUMGRID('R',n)) generates the 5-point discrete Laplacian.
The regions currently available are:
'S' - the entire square.
'L' - the L-shaped domain made from 3/4 of the entire square.
'C' - like the 'L', but with a quarter circle in the 4-th square.
'D' - the unit disc.
'A' - an annulus.
'H' - a heart-shaped cardioid.
'B' - the exterior of a "Butterfly".
'N' - a nested dissection ordering of the square.
To add other regions, edit toolbox/matlab/demos/numgrid.m.
See also: DELSQRAP3GV, DELSQSHOW , DELSQDEMO .