Forward difference: Difference between revisions

=={{header|Stata}}==

It's possible to implement differences using row indices. For instance, first forward differences of a variable x can be defined by:

<lang stata>gen y=x[_n+1]-x[_n]</lang>

However, it's much more natural to use [http://www.stata.com/help.cgi?tsvarlist time-series varlists]. In order to use them, it's necessary to first set a ''time'' variable, which may be simply an index variable.

<lang stata>* First create a dataset

clear all

set obs 100

gen i=_n

tsset i

gen x=rnormal()

* Differences

display "Difference order?" _request(k)

gen y=D${k}F${k}.x</lang>