# fourlap.m

Fourier spectral representation of the Laplacian acting on a 3D data array.

## Syntax

    L=fourlap(npoints,extents)


## Description

Fourier spectral differentiation operators are exact on a given grid when the data array satisfies the Larmor condition on that grid.

## Arguments

    npoints -  a three-element vector specifying the number of
discretization points in each dimension of the
3D cube of data that the operator will be acting
on, ordered as [X Y Z].

extents -  a three-element vector specifying axis extents,
ordered as [X Y Z].


## Outputs

    L - Fourier spectral Laplacian, a sparse matrix designed to act
on the vectorization of the 3D data array. The dimensions of
the data array are assumed to be ordered as [X Y Z].


## Notes

Periodic boundary conditions.