save an algorithm and call it

hello all

I want to save the Thomas algorithm and backward substitution algorithm and call it whenver I need it in my code. How to do this?

solving linear system with Thomas algorithm*******************************
  for k = 1:p-1
i = k +1;
l(i,k)=Ac(i,k)/Ac(k,k);
for j = k :k+1
Ac(i,j) = Ac(i,j)- l(i,k)*Ac(k,j);
end
b(i) = b(i)-l(i,k)*b(k);
  end
   %apply backward substitution
for k = p:-1:1
g(k)=b(k);
for j=k+1: min(p,k+1)
    g(k)=g(k)-Ac(k,j)*g(j);
end
g(k)=g(k)/Ac(k,k);

end
T_cn(2:n-1)=g(1:p);
 end
    

[Rik]

Do you mean you want to make this a function?

[Nima Vali]

Yes, I want to call it like z=thomas(Ac,b,p-2);

Answer 1

[Rik]

Store this in thomas.m

function z=thomas(Ac,b,p_minus_2)
%solving linear system with Thomas algorithm
%
% More explanation about this function and its syntax go here.
p=p_minus_2+2;

for k = 1:p-1
    i = k +1;
    l(i,k)=Ac(i,k)/Ac(k,k);
    for j = k :k+1
        Ac(i,j) = Ac(i,j)- l(i,k)*Ac(k,j);
    end
    b(i) = b(i)-l(i,k)*b(k);
end

%apply backward substitution
for k = p:-1:1
    g(k)=b(k);
    for j=k+1: min(p,k+1)
        g(k)=g(k)-Ac(k,j)*g(j);
    end
    g(k)=g(k)/Ac(k,k);
end
T_cn(2:n-1)=g(1:p);

end
    

[Nima Vali]

Thanks very much!