# fdmat.m

From Spinach Documentation Wiki

Returns arbitrary-order central finite-difference differentiation matrices (sparse) with unit grid point spacing.

## Contents

## Syntax

D=fdmat(dim,nstenc,order,boundary)

## Arguments

dim - dimension of the column vector to be differentiated nstenc - number of points in the finite diffe- rence stencil order - order of the derivative required boundary - 'wall' fills the edges with sided finite difference schemes, 'pbc' assumes periodic boundaries. The default is 'pbc'.

## Outputs

D - finite difference differentiation matrix

## Examples

A three-point second derivative matrix designed to act on a vector with ten elements with periodic boundary conditions is:

>> full(fdmat(10,3,2,'pbc')) ans = -2 1 0 0 0 0 0 0 0 1 1 -2 1 0 0 0 0 0 0 0 0 1 -2 1 0 0 0 0 0 0 0 0 1 -2 1 0 0 0 0 0 0 0 0 1 -2 1 0 0 0 0 0 0 0 0 1 -2 1 0 0 0 0 0 0 0 0 1 -2 1 0 0 0 0 0 0 0 0 1 -2 1 0 0 0 0 0 0 0 0 1 -2 1 1 0 0 0 0 0 0 0 1 -2

## See also

fdvec.m, fdlap.m, fdhess.m, fdkup.m, fdweights.m, fftdiff.m, fourdif.m, fourlap.m

*Version 2.2, authors: Ilya Kuprov*