IRIS Toolbox Reference Manual

## diff

First difference pseudofunction

#### Syntax

    diff(EXPR)
    diff(EXPR,K)

#### Description

If the input argument `K` is not specified, this pseudofunction expands to

    ((EXPR)-(EXPR{-1}))

If the input argument `K` is specified, it expands to

    ((EXPR)-(EXPR{K}))

The two derived expressions, `EXPR{-1}` and `EXPR{K}`, are based on `EXPR`, and have all its time subscripts shifted by --1 or by `K` periods, respectively.

#### Example

These two lines

    diff(Z)
    diff(log(X{1})-log(Y{-1}),-2)

will expand to

    ((Z)-(Z{-1}))
    ((log(X{1})-log(Y{-1}))-(log(X{-1})-log(Y{-3})))

IRIS Toolbox. Copyright © 2007—2013 Jaromir Benes.