w = conv(u,v) returns the convolution of vectors u and v. If u and v are vectors of polynomial coefficients, convolving them is equivalent to multiplying the two polynomials.
w = conv(u,v,shape) returns a subsection of the convolution, as specified by shape. For example, conv(u,v,'same') returns only the central part of the convolution, the same size as u, and conv(u,v,'valid') returns only the part of the convolution computed without the zero-padded edges.
w = conv(u,v) w = conv(u,v,shape)
u = [1 1 1]; v = [1 1 0 0 0 1 1]; w = conv(u,v)
w = 1 2 2 1 0 1 2 2 1