matlab中的求导函数diff

2018-01-19

今天发现我的标题写错了，diff不知怎么写成了fill，醉醉醉

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matlab中用函数diff做求导

函数描述：DIFF Difference and approximate derivative.

语法格式：

Y = diff(X)Y = diff(X,n)Y = diff(X,n,dim)

1.  Y = diff(X)

  (1).  DIFF(X), for a vector X, is [X(2)-X(1)  X(3)-X(2) ... X(n)-X(n-1)].

X是长度为n容器，也就是长度为n的行向量，返回n-1长度的行向量，后一个数减去前一个数

   (2).  DIFF(X), for a matrix X, is the matrix of row differences,       [X(2:n,:) - X(1:n-1,:)].

 X是个n行的矩阵，返回结果是n-1行的矩阵，后一行数减去前一行数

   (3). DIFF(X), for an N-D array X, is the difference along the firstnon-singleton dimension of X.

这个不大会，以后回了在更新吧，不过意思跟前面应该差不多。

  （4）.还有一种是单个点的导数值

      diff(X,N) is the N-th order difference along the first non-singleton       dimension (denote it by DIM). If N >= size(X,DIM), diff takes        successive differences along the next non-singleton dimension.

n是求导阶数

3.  diff(X,N,DIM)

diff(X,N,DIM)is the Nth difference function along dimension DIM.       If N >= size(X,DIM), diff returns an empty array.

求导阶数不能大于DIM