> Chris Rohlfs
> >
> > i'm trying to figure out the macro basics & can't seem to
> > find any simple
> > examples on the web or in the manual. if someone could
> > please post the
> > text of a simple *.do file that uses macros, i'd really
> > really appreciate
> > it. i'm using stata 7.
> >
> > i'd also really appreciate any suggestions on my specific
> > problem that i'm
> > trying to solve w/ macros:
> >
> > to take variables (air_reg1, air_reg2, ..., air_reg24)
> > and (voc_reg1, ..., voc_reg24)
> >
> > and to produce the sum of the products:
> >
> > air_reg1*voc_reg1 + air_reg2*voc_reg2 + ... + air_reg24*voc_reg24
> >
> > for a bunch of different sets of variables ({air,voc} is
> > one example) w/ a
> > large dataset.
There is a sequel. It could be,
as Bill Gould reminded me the other day,
that this kind of problem is better tackled
with a -reshape-.
Your data are wide, in -reshape-'s jargon.
If you -reshape- to long, something like
reshape long air_reg voc_reg <others> , i(id)
then calculate a product just once
gen p_air_reg_voc_reg = air_reg * voc_reg
and then the sum of the products
bysort id : egen double sp_air_reg_voc_reg = sum(p_air_reg_voc_reg)
The advantage of this is that other sums of products
are equally easy.
Once this is done, -reshape- back again.
For more details, see [R] reshape and, if need be,
http://www.stata.com/support/faqs/data/reshape3.html
Nick
[email protected]
*
* For searches and help try:
* http://www.stata.com/support/faqs/res/findit.html
* http://www.stata.com/support/statalist/faq
* http://www.ats.ucla.edu/stat/stata/
