covn函数

covn函数：

主要进行N维上的卷积，就是【 m n k】三维矩阵上的卷积

N-dimensional convolution

Syntax

• C = convn(A,B)
  C = convn(A,B,'shape')
  

Description

C = convn(A,B) computes the N-dimensional convolution of the arrays A and B. The size of the result is size(A)+size(B)-1.

C = convn(A,B,'shape') returns a subsection of the N-dimensional convolution, as specified by the shape parameter:

对边界处理的三种形式：

'full'	Returns the full N-dimensional convolution (default).
'same'	Returns the central part of the result that is the same size as A.
'valid'	Returns only those parts of the convolution that can be computed without assuming that the array A is zero-padded. The size of the result is  max(size(A)-size(B) + 1, 0)