diff

Difference and discrete derivative

Calling Sequence

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)