Otherwise put, as I see it:
In the context of -forvalues- `maxn'
is a variable _name_ and 1/__000001 is unacceptable
as an argument.
In the context of -display- Stata leans over backwards
to find a single something that can be displayed and, as
Richard says, first sees the variable name and then
jumps to displaying its value for the first observation.
forvalues i = 1/`=`maxn'[1]' {
}
is another way to do it, but not as good as directly
through -summarize-. (For this purpose, -summarize, meanonly-
would be even better.)
Nick
[email protected]
Richard Williams
> At 05:00 PM 7/16/2005 -0700, Brian R. Sala wrote:
> >Can someone enlighten me on this syntax error, please.
> >
> >why does this fail:
> >
> >. tempvar maxn
> >
> >. egen byte `maxn' = max(assignment_count)
> >
> >. tab `maxn'
> >
> > __000001 | Freq. Percent Cum.
> >------------+-----------------------------------
> > 4 | 20,299 100.00 100.00
> >------------+-----------------------------------
> > Total | 20,299 100.00
> >
> >. forvalues i = 1/`maxn' {
> > 2. di `i'
> > 3. }
> >invalid syntax
> >r(198);
> >
> >
> >clearly, `maxn' has a value. Superficially, this looks
> equivalent to the
> >syntax shown in the STATA 8 programming manual (pp. 206-207).
>
> Actually, `maxn' is a variable and hence every case has a value for
> it. All cases may have the same value on the variable, but
> it is still a
> variable. forvalues doesn't like you specifying a variable
> here, it wants
> a single number.
>
> >yet when I do this:
> >
> >. tempvar max_assignments
> >. egen byte `max_assignments' = max(assignment_count)
> >. local maxn = `max_assignments'
> >. forvalues i = 1/`maxn' {
> > 2. display `i'
> > 3. }
> >1
> >2
> >3
> >4
>
> Here, `maxn' is a constant and not a variable; what the local
> statement has
> done is set it equal to the value the first case has on
> `max_assignments'. Since every case has the same value on
> `max_assignments' you are fine, but if `max_assignments' had
> different
> values you could be in trouble if the first case didn't have
> the value you
> want.
>
> To further see this:
>
> . webuse auto
> (1978 Automobile Data)
>
> . local maxn = price
>
> . di `maxn'
> 4099
>
> 4099 is the value of the first case for price.
>
> . sort length
>
> . local maxn = price
>
> . di `maxn'
> 3895
>
> After sorting, we now have a different value for the first
> case and hence
> `maxn' now has a different value.
>
> Perhaps a more common way to get what you want is to do
> something like this:
>
> . sum price
>
> Variable | Obs Mean Std. Dev. Min
> Max
> -------------+--------------------------------------------------------
> price | 74 6165.257 2949.496 3291
> 15906
>
> . return list
>
> scalars:
> r(N) = 74
> r(sum_w) = 74
> r(mean) = 6165.256756756757
> r(Var) = 8699525.974268789
> r(sd) = 2949.495884768919
> r(min) = 3291
> r(max) = 15906
> r(sum) = 456229
>
> . local maxn = r(max)
>
> . di `maxn'
> 15906
>
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