% A2=mkA2(J,mu,theta)
%
% Make the matrix for the explicit part of the theta method.

function A2=mkA2(J,mu,theta)
    A2=zeros(J-1);
    for j=1:J-1
        A2(j,j)=1-2*mu*(1-theta);
    end
    for j=1:J-2
        A2(j,j+1)=mu*(1-theta);
        A2(j+1,j)=mu*(1-theta);
    end
