MassAssembler1D.m

function M = MassAssembler1D(x)
% See book §1.5.1.

n = length(x)-1; % number of subintervals
M = zeros(n+1,n+1); % allocate mass matrix
for i = 1:n % loop over subintervals
h = x(i+1) - x(i); % interval length
M(i,i) = M(i,i) + h/3; % add h/3 to M(i,i)
M(i,i+1) = M(i,i+1) + h/6;
M(i+1,i) = M(i+1,i) + h/6;
M(i+1,i+1) = M(i+1,i+1) + h/3;
end

end