MATLAB help, LaGrange interpolation.

hallaballooo

Does anyone know how to write a matlab program to compute lagrange interpolation? I have a set of data and I want to estimate the value of the data between points using LaGrange. I put this code together:
function P = pollly(N,x,y,input)
N = N+1;
X = 0;
for j = 1:N
X = X + y(j) * lagrange(N,j,x,input);
end
P = X;



function L = lagrange(N,j,x,guess)
L = 1;
for i = 1:N
if (i ~= j)
L = L * ( guess - x(i) ) / ( x(j) - x(i) );
end
end



But it doesnt work at all. Can someone please help?

shwaip

doesn't work as in:

a) doesn't give the right answer
b) gives errors
c) other

hallaballooo

shwaip wrote:

doesn't work as in:

a) doesn't give the right answer
b) gives errors
c) other

Doesnt give the right answers.

shwaip

I found several examples by searching google for matlab lagrange interpolation. perhaps you could try one of those.

sedo0o

shwaip wrote:

doesn't work as in:

a) doesn't give the right answer
b) gives errors
c) other

it says :
??? function P = pollly(N,x,y,input)
|
Error: Function definitions are not permitted at the prompt or in scripts.

plzzzz suggest another code if this is not valid

shwaip

what are you trying to do?

The code in the first post didn't work for the first guy...