Using functions relating polynomial

Hi guys,

I would like to develop a function called poly_prod which determines the product of two polynomials. Let say P=[1 1 -7 -15] and Q=[3 -1 2], and when I use poly_prod(P,Q), the following answer is expected.

First Q(1)*P, which is [3 3 -21 -45]

Second Q(2)*P, which is [-1 -1 7 15]

Third Q(3)*P, which is [2 2 -14 -30]

Then it should be added like this:

[3 3 -21 -45 0 0] + [0 -1 -1 7 15] + [0 0 2 2 -14 -30]

and the final answer should show: [3 2 -20 -36 1 -30]

Thank you.

[Rik]

What have you tried so far? It sounds like a relatively easy function to implement with a loop. And it sounds like homework, so I've added the tag.

[Vellan]

Thanks for the reply.

This is what I have done so far

function ret=poly_prod(P1,P2)
n=poly_row(P1)
m=poly_row(P2)
a=size(n)                  
b=size(m)                   
ret=[];
   for n=1:b(2)
       ret=[ret P1*P2(n)]
   end
end

The polyrow is a function that I created to make sure the polynomial is in a row vector.

I don't know how to carry on from this.

Answer 1

[Matt J]

result = conv(P,Q)

[Vellan]

Thanks Matt. It works.