MATLAB Function Reference Volume 1: A - E - Bad Request

del2
2-414
-L = del2(U) when U is an multidimensional array, returns an
approximation of
where N is ndims(u).
Examples The function
L = del2(U,h) where H is a scalar uses H as the spacing between points in each
direction (h=1 by default).
L = del2(U,hx,hy) when U is a rectangular array, uses the spacing specified
by hx and hy. If hx is a scalar, it gives the spacing between points in the
x-direction. If hx is a vector, it must be of length size(u,2) and specifies the
x-coordinates of the points. Similarly, if hy is a scalar, it gives the spacing
between points in the y-direction. If hy is a vector, it must be of length
size(u,1) and specifies the y-coordinates of the points.
L = del2(U,hx,hy,hz,...) where U is multidimensional uses the spacing
given by hx, hy, hz, ...
has
∇ 2 u
----------
2N
uxy ( , ) x2 y2 = +
∇ u 2 =
4
For this function, 4*del2(U) is also 4.
[x,y] = meshgrid(-4:4,-3:3);
U = x.*x+y.*y
U =
25 18 13 10 9 10 13 18 25
20 13 8 5 4 5 8 13 20
17 10 5 2 1 2 5 10 17
16 9 4 1 0 1 4 9 16
17 10 5 2 1 2 5 10 17
20 13 8 5 4 5 8 13 20
25 18 13 10 9 10 13 18 25