diff

Scilab Function
Last update : 07/04/2004

diff - Difference and discrete derivative

### Calling Sequence

  `y=diff(x)`
  `y=diff(x [,n [,dim]])`

### Parameters

- `x`: vector or matrix (real, complex, sparse or polynomial)
- `n`: integer the order of differentiation
- `dim`: integer or character string with values "r","c" and "*"
- `y`: scalar or vector

### Description

`y=diff(x)` compute the difference function y=x(2:$)-x(1:$-1)

`diff(x,n,dim)` is the `n` th difference function along dimension `dim`.

`diff(x,n,"*")` is equivalent to diff(x(:),n).

Default value for `n` is 1. Default value for `dim` is `"*"`.

`dim='r'` is equivalent to `dim=1` and `dim='c'` is equivalent to `dim=2`.

### Examples

    v=(1:8)^3;
    diff(v)
    diff(v,3)

    A=[(1:8)^2
       (1:8)^3
       (1:8)^4];

    diff(A,3,2)

    //approximate differentiation
    step=0.001
    t=0:step:10;
    y=sin(t);
    dy=diff(sin(t))/step; //approximate differentiation of sine function
    norm(dy-cos(t(1:$-1)),%inf)