Generate lags, leads, and differences                             (STB-7: sts2)
-------------------------------------

	^lag^  [#] varname [^, s^uffix^(^str^)^]

	^lead^ [#] varname [^, s^uffix^(^str^)^]

	^dif^  [#] varname [^, s^uffix^(^str^)^]


Description
-----------

^lag^ generates the lags of varname.  # specifies the number of lags to be gen-
erated and 1 is assumed if # is not specified.  "^lag 2 gnp^" creates ^L.gnp^ and
^L2.gnp^.

^lead^ generates leads of varname.  # specifies the number of leads to be gen-
erated and 1 is assumed if # is not specified.  "^lead 2 gnp^" creates ^F.gnp^ and
^F2.gnp^.


Description, continued
----------------------

In either case, # may be specified as negative, in which case ^lag^ produces 
leads and ^lead^ produces lags.  # may be specified as 0, in which case ^lag^
and ^lead^ do nothing.

^dif^ generates the #th difference of varname.  "^dif gnp^" creates ^D.gnp^.
"^dif 2 gnp^" creates ^D2.gnp^, the difference in the difference, but does not
create ^D.gnp^.  # must be greater than or equal to 0; if # is 0, ^dif^ does 
nothing.



Options
-------

^suffix(^str^)^ specifies the base part of the name to be used rather than the 
    existing name.  E.g., "^lag 2 gnp, suffix(x)^" creates variables named ^L.x^
    and ^L2.x^ rather than naming the variables ^L.gnp^ and ^L2.gnp^.




Examples 
--------

 . ^lag gnp^
 . ^lag 2 gnp^
 . ^lag 4 gnp^
 . ^lag -2 gnp^

 . ^lead 2 gnp^

 . ^dif gnp^
 . ^dif 2 gnp^


Remarks
-------

"^lag gnp^" creates ^L.gnp^.  "^lag 2 gnp^" creates ^L.gnp^ and ^L2.gnp^.  Therefore,
you may reason that you cannot type "^lag 2 gnp^" after "^lag gnp^" because the
variable ^L.gnp^ already exists.  You may, however.


Operators may be applied to results of other operators, for instance:


Remarks, continued
------------------

 . ^dif gnp^
 . ^lag D.gnp^

The resulting variable is ^LD.gnp^.  However, the routines are not smart about
combining names:

 . ^lag gnp^
 . ^lag L.gnp^

creates a variable named ^LL.gnp^, not ^L2.gnp^.


Also note that

 . ^lag gnp^
 . ^lead L.gnp^

produces ^FD.gnp^, which is not quite identical to ^gnp^ because the last observa-
tion will be missing.



Author
------
 
Sean Becketti, Federal Reserve Bank of Kansas City.


Also see
--------

    STB:  sts2 (STB-7)
On-line:  ^help^ for ^dropoper^, ^growth^