> use "`mytempfile'"
> display _N
> local x _N
> display `x'
>
> will have the same effect as
>
> use "`mytempfile'"
> display _N
> local x=_N
> display `x'
>
> The effect is that the display command will twice show the
> right number, 17,
> in both cases.
>
> The difference between two slabs of code is that
>
> forvalues i=1/`x'
>
> does not work after the first, but works fine after the second.
>
> In other words, the equal sign makes no difference to the
> value of the local
> variable x, yet it does matter to forvalues.
>
Following up on Nick Cox's point, in fact, the first and second approach
*DO NOT* put the same thing into the local macro x. In the first case,
the local macro contains the literal string _N. In the second case, the
local macro contains the number 17 (or whatver the number of
observatrions happens to be).
In the first case, when you say
display `x'
this is substituted to
display _N
by stata (because `x' has the value _N), and then the display command
evaluates _N to be 17.
Compare:
local x _N
di "`x'"
with
local x=_N
di "`x'"
to see what is really in the local macro, without further substitution
by the display command.
Nick Winter
*
* 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/
