RE: st: Appending several files

[David Kantor <kantor.d@att.net>]

Thanks, Nick, for your comments and your alternative suggestion.

At 08:01 AM 10/16/2006, you wrote:
[...]

> 2. As you want the numeric interpretation, I find
>
> local j = 0
>
> clearer, particularly as you are testing its
> numeric value later. Stata doesn't care, but
> a code reader might.
Yes, indeed, but we are also told, understandably, that
local j "0"
is more efficient.  But it is a minor inconvenience for Stata to 
process -local j = 0-.  Furthermore, if I had been really attentive 
to the fact the j is a number, then I would have used scalars 
instead.  But I use macros to make use of the ++ operator.  I don't 
believe that it applies to scalars.  (??)


> 3. If you are a Windows user and accustomed
> to putting spaces in your filenames, this will
> fall over unless the names come quoted.
Yes, indeed.  But I am not one to use spaces in file names, so I 
hadn't thought of that. (I find them a bit of an anathema.  But they 
are with us now, at least among Windows users, and there's no turning 
back. I suppose they are a feature that was created to make computers 
more accessible to the Muggles.)


> I feel queasy about going through two loops
> simultaneously unless it's unavoidable.
> That's mostly just a style prejudice.
[...]
I hadn't even thought of it as two loops simultaneously.  I think of 
it as one loop with f as the driver; j is a "passenger". It is not 
unusual, in general programming, to have many "passenger" variables 
in a loop, each acquiring new values in each iteration.

Another matter: I used the "number" j as a convenient way to tell 
whether you are in the first iteration. You don't really need to know 
the iteration count; the real issue is whether the loop is in the 
first iteration. Thus you can do:

local first = 1
foreach f in `r(files)' {
if `first' {
 use `f'
 local first = 0
}
else {
 append using `f'
}

Also, Paul Seed had another interesting technique.

--David

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