Lagrange polynomial giving me Inf in final form

Can this be resolved?

[KSSV]

You are multiplying with Inf..? Copy the whole code here don't attach as a image snippet.

[Steve Avilesmejia]

clc,clear all, format compact

sp = [30 45 60 75 90 120];

mb = [2 4 9 17 27 82];

n=length(sp)-3;

syms x;

Q = 0;

for i = 1:n+1

M = 1;

for j = 1: n+1

if j~=1

M = M * (x - sp(j))/(sp(i)-sp(j));

end

end

Q = Q + mb(i)*M;

end

Q

[Vladimir Sovkov]

With i-j, this code performs a division by zero, producing Inf.

[Steve Avilesmejia]

im just not sure why it is coming out as an "Inf".

[Steve Avilesmejia]

In this case does this code not work or is there a way around it?

Answer 1

[KSSV]

% clc; clear all ;
sp = [30 45 60 75 90 120];
mb = [2 4 9 17 27 82];
n=length(sp)-3;
syms x;
Q = 0;
for i = 1:n+1
    M = 1;
    for j = 1: n+1
        if j~=i
            M = M * (x - sp(j))/(sp(i)-sp(j));
        end
    end 
    Q = Q + mb(i)*M;
end