Multiplying two vectors together

I'm trying to write a function that takes 2 polynomials as inputs and multiplies them together. the two inputs have to be in vector form. 5x^2+7x+8 means you would type in [5 7 8]. i want the output to be in vector form.

[Walter Roberson]

Okay, but you have not asked a question.

How would you do it if you were doing the multiplication by hand?

Answer 1

[Fangjun Jiang]

You need the conv() function.

http://www.mathworks.com/help/techdoc/ref/conv.html

Answer 2

[Andrei Bobrov]

youfunction = @(p1,p2)conv(p1,p2)

or [ edit 10/24/2011 09:14 MSD ]

function out = yourfunction(p1,p2)
m = numel(p1);
n = numel(p2);
A = bsxfun(@minus,1:m+n-1,(0:n-1)');
A(A<1|A>m)=1;
out = p2*tril(triu(p1(A)),m-1);

more variant [ add 10/24/2011 11:41 MSD ]

function out = yourfunction(p1,p2)
m = numel(p1);
n = numel(p2);
A = zeros(n,m+n-1);
A(bsxfun(@plus,1:n:(n-1)*m,(0:n+1:(n^2-1))')) = ones(n,1)*p1;
out = p2*A;