Continuing Matrix involving a function to make very large

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Hi all, i have a typed square matrix and need to expand it to be very large how ever this will take far too long to do manually. my matrix code is below please help if you know any function to expend it while keeping the same pattern.
thanks in advance
syms e P n
c=1;
G(n)=e/(2*(P+0.5*(1i*n*c)-(0.25*(n)^2)));
j=[1 0 G(7) 0 0 0 0 0 0 0 0 0 0 0 0;0 1 0 G(6) 0 0 0 0 0 0 0 0 0 0 0; G(5) 0 1 0 G(5) 0 0 0 0 0 0 0 0 0 0; 0 G(4) 0 1 0 G(4) 0 0 0 0 0 0 0 0 0; 0 0 G(3) 0 1 0 G(3) 0 0 0 0 0 0 0 0; 0 0 0 G(2) 0 1 0 G(2) 0 0 0 0 0 0 0; 0 0 0 0 G(1) 0 1 0 G(1) 0 0 0 0 0 0 ; 0 0 0 0 0 G(0) 0 1 0 G(0) 0 0 0 0 0; 0 0 0 0 0 0 G(-1) 0 1 0 G(-1) 0 0 0 0; 0 0 0 0 0 0 0 G(-2) 0 1 0 G(-2) 0 0 0; 0 0 0 0 0 0 0 0 G(-3) 0 1 0 G(-3) 0 0; 0 0 0 0 0 0 0 0 0 G(-4) 0 1 0 G(-4) 0; 0 0 0 0 0 0 0 0 0 0 G(-5) 0 1 0 G(-5); 0 0 0 0 0 0 0 0 0 0 0 G(-6) 0 1 0; 0 0 0 0 0 0 0 0 0 0 0 0 G(-7) 0 1 ];

回答(1 个)

Ameer Hamza
Ameer Hamza 2020-6-17
Try this
syms e o n
c=1;
P = 1;
G(n)=e./(2.*(P+0.5*(1i*n.*c)-(0.25*(n)^2)));
N = 15;
l_start = 5;
u_start = 7;
l_end = l_start-N+3;
u_end = u_start-N+3;
j = diag(ones(1,N)) + diag(G(l_start:-1:l_end), -2) + diag(G(u_start:-1:u_end), 2);

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