Question

Can anyone please help me to write this matlab m-file?
Here is the pseudocode :
http://oi53.tinypic.com/u1pvc.jpg

Answer 1

function y=lgrng(x,y,i,j)

sum = 0 ;
while i = 0,n
product = yi;
while j = 0,n
if a ~= b
then
product = product * ( x - xj ) / (xi - xj)
end
end
sum = sum + product;
end
print sum;
end

Answer 2

this is what i tried to write,too bad it didn t work.

Answer 3

Of course not, you tried to paste the algorithm into a .m without regard to Matlab syntax and the picture algorithm is badly written. I can't tell if it means a do while or for loop or what types of inputs you are using (vectors, constants, etc).

Answer 4

I'll get you started off, but I have no idea about you are attempting to accomplish, what test cases you have, what the inputs are or what information you have about this. You have two inputs with the same name. I recommend including better info in the future...

function sum = test(x, y, n)
% assuming y is a vector
% assuming x is a vector

sum = 0;

for i = 1 : n
product = y(i);
for j = 1 : n
if i ~= j
product = product .* (x - x(j)) ./ (x(i) - x(j))
end
end
sum = sum + product;
end

return

Answer 5

It seems from the picture that there is another parameter 'X'. you should name it differently as JD pointed out. otherwise this line 'product = product .* (x - x(j)) ./ (x(i) - x(j))' won't work.
Try change x into x1 and include it into the function at the first line.
Good luck

Answer 6

Assuming x is a vector, you are subtracting a scalar from a vector (which is fine), dividing a vector by a scalar (which is fine) and multiplying each vector element by a scalar (which is fine).

Answer 7

yeah, but can't figure out what this function is trying to do.
This is a real problem.

Answer 8

hi guys,sorry for the late reply,thank you very much for your help.
and here is the whole question: http://oi55.tinypic.com/20r4ryp.jpg