In previous versions of matlab, the augmented matrix was used by

sparse linear equation solvers, \ and /, for nonsquare problems,

but now MATLAB performs a least squares solve using the qr

factorization of A instead.

See also spparms.

Reference page in Help browser

doc spaugment

<numgrid> - Number the grid points in a two dimensional region.

NUMGRID Number the grid points in a two dimensional region.

G = NUMGRID(REGION,N) numbers the points on an N-by-N grid in

the subregion of -1<=x<=1 and -1<=y<=1 determined by REGION.

SPY(NUMGRID(REGION,N)) plots the points.

DELSQ(NUMGRID(REGION,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.

See also delsq, DELSQSHOW, delsqdemo.

<delsq> - Construct five-point finite difference Laplacian.

DELSQ Construct five-point finite difference Laplacian.

delsq(G) is the sparse form of the two-dimensional,

5-point discrete negative Laplacian on the grid G.

The grid G can be generated by NUMGRID or NESTED.

See also numgrid, del2, delsqdemo.