tdma subscript zero problem

function x=TDMAsolver(a,b,c,d)
% a, b, c are coloumn vectors for compressed tridiagonal matrix, d is the
% right vector
 %n is the number of rows
n = length(b);
% Modify the first row cofficients
c(1)=c(1)/ b(1); % Division by zero risk.
d(1)=d(1)/b(1);  % division by zero would imply a singular matrix

for i=2:n-1;
    temp=b(i)-a(i)*c(i-1);
    c(i)=c(i)/temp;
    d(i)=(d(i)-a(i)*d(i-1))/temp;
end

d(n)=(d(n)-a(n)*d(n-1))/(b(n)-a(n)*c(n-1));
%back to substitute 
x(n)=d(n);
for i =n-1:-1:1
    x(i)=d(i)-c(i)*x(i+1);
end
end

i have a problem in running this====

Attempted to access d(0); index must be a positive integer or logical.

Error in TDMAsolver (line 16)
d(n)=(d(n)-a(n)*d(n-1))/(b(n)-a(n)*c(n-1));

Answer 1

[Walter Roberson]

If n = length(b) is 1, then when you try to access d(n-1) or c(n-1) in (d(n)-a(n)*d(n-1))/(b(n)-a(n)*c(n-1)) then you would have a problem.