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| function [x,D]=fddif(N,order,pts);
% build equispaced grid on [-1,1], and
% five points finite diference matrix for N mesh points
%pts=5;
x=linspace(-1,1,N)';
h=x(2)-x(1);
% subroutine for finite difference weights
W=ufdwt(h,pts,order);
t=(pts+1)/2;
%central difference in the middle
D=spdiags(ones(N,1)*W(t,:),-t+1:t-1,N,N);
for indd=1:t-1
D(indd,1:pts)=W(indd,:); % at the left boundary
D(N-indd+1,end-pts+1:end)=W(end-indd+1,:); % at the right boundary
end
|
