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# diff

Difference and discrete derivative

### Syntax

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

### Arguments

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/matrix

### 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)```

• interp — cubic spline evaluation function
• interp2d — bicubic spline (2d) evaluation function
• splin — cubic spline interpolation
• eval_cshep2d — bidimensional cubic shepard interpolation evaluation
• numderivative — approximation des dérivées d'une fonction (matrices jacobienne ou hessienne)