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diff

Difference and discrete derivative

Syntax

y = diff(x)
y = diff(x, n)
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 nth 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)

See also


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