That could be condensed to
bysort year state cnum (votes) : keep if _n == _N
-search by- points to a discursive tutorial, accessible to all:
SJ-2-1 pr0004 . . . . . . . . . . Speaking Stata: How to move step
by: step
Q1/02 SJ 2(1):86--102 (no
commands)
explains the use of the by varlist : construct to tackle
a variety of problems with group structure, ranging from
simple calculations for each of several groups to more
advanced manipulations that use the built-in _n and _N
The important thing is that the parentheses notation is _not_ cosmetic
here.
Nick
[email protected]
Ashim Kapoor
I made a "silly" mistake. I realized it only some time ago.
What I wanted to do was : -
sort year state cnum votes
and then ONLY do
by year state cnum : keep if _n==_N
This would bring out the item with the max no of votes in a year in a
state in a contituency.
I erred and thought that I should do by year state cnum VOTE : keep if
_n==_N.
On Tue, Sep 16, 2008 at 8:09 PM, Nick Cox <[email protected]> wrote:
> Neil Shephard and Martin Weiss made helpful comments.
>
> My guess is that what Ashim needs is
>
> bysort year state cnum (votes) : keep if _n == _N
>
> except that his report "I have ." leads me to guess that he has
missing
> values, which would be problematic with that code.
>
> Missing values are sorted to the end of any block of observations, as
> they are treated as arbitrarily large. So missing values will show up
in
> the kept data for every constituency (if that is what -cnum- indexes)
> for which they exist.
>
> Even if this guess is correct, it raises two questions.
>
> 1. Why does Ashim have missings? Are they something else, e.g. zeros?
If
> so, they should be fixed.
>
> 2. If the missings are genuine, they need to be fixed before
-sort-ing.
> Ashim's purpose seems to call for
>
> drop if missing(votes)
>
> Also -search dropmiss-.
>
> Nick
> [email protected]
>
> Ashim Kapoor
>
> I want to do the following :
>
> sort year state cnum votes
>
> by year stata cnum votes : keep if _n==_N
>
> That way I get the guy with the max no of votes.
>
> Now when I do this for 1 or 2 arguments for by then it works, but not
> for 4 arguments I have . Does by have a limit on how many arguments it
> can have ?
>
> I read -help by- and that does mention using by in the following
> fashion : -- > by year ( state) . Do I need to put in brackets for the
> other arguments?
>
> Could someone please clarify?
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