conv.sci

来自「小波分解源代码」· SCI 代码 · 共 39 行

function c = conv(a, b)
//CONV Convolution and polynomial multiplication.
//   C = CONV(A, B) convolves vectors A and B.  The resulting
//   vector is length LENGTH(A)+LENGTH(B)-1.
//   If A and B are vectors of polynomial coefficients, convolving
//   them is equivalent to multiplying the two polynomials.
//
//   See also DECONV, CONV2, CONVN, FILTER and, in the Signal
//   Copyright Aldo I Maalouf


na = length2(a);
nb = length2(b);

if na ~= prod(size(a)) | nb ~= prod(size(b))
  error('A and B must be vectors.');
end

// Convolution, polynomial multiplication, and FIR digital
// filtering are all the same operations.  Since FILTER
// is a fast built-in primitive, we'll use it for CONV.

// CONV(A,B) is the same as CONV(B,A), but we can make it go
// substantially faster if we swap arguments to make the first
// argument to filter the shorter of the two.
if na > nb
    if nb > 1
        a(na+nb-1) = 0;
    end
    c = mtlb_filter(b, 1, a);
else
    if na > 1
        b(na+nb-1) = 0;
    end
    c = mtlb_filter(a, 1, b);
end

endfunction