Notice: On April 23, 2014, Statalist moved from an email list to a forum, based at statalist.org.

# RE: st: histogram

 From Schöler, Lisa To "statalist@hsphsun2.harvard.edu" Subject RE: st: histogram Date Thu, 14 Oct 2010 14:17:35 +0000

```Thank you

-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Maarten buis
Sent: Thursday, October 14, 2010 4:14 PM
To: statalist@hsphsun2.harvard.edu
Subject: Re: st: histogram

--- On Thu, 14/10/10, Schöler, Lisa wrote:
> Now I need to get a histogram that uses only one
> observation for each id for the mean(brand). Therefore I
> wanted to include a dummy=1, so I can use the command
>
> . histogram if dummy==1
>
> Can anybody help me how I can create a dummy=1 only for one
> observation per id? I was gonna use
>
> . by id: gen dup = cond(_N==1,0,_n)
>
> and then
>
> . histogram if dup==1
>
> But the problem here is that I have missings within my id
> groups, so sometimes my dup per id starts with 2.

If you create your mean variable using -egen- then you won't
get missing values, thus preventing the entire problem.

Alternatively, you can ask Stata to sort within each id on
mean, and pick the first observation. A missing value is in
Stata a very large number, so they will in that case be the
last observation.

*------------- begin example --------------
drop _all
input id   brand  year
1   7      1999
1   5      2000
1   3      2001
1   5      2002
1   .      2003
2   .      1999
2   7      2000
2   8      2001
2   5      2002
2   4      2003
3   .      1999
3   7      2000
3   8      2001
3   5      2002
3   4      2003
end
egen mean = mean(brand), by(id)
list
// no missing values, so that solves the problem

// lets create a missing value, and solve your
// problem than:
replace mean = . in 1
bys id (mean) : gen byte mark = _n == 1 if _N > 1
list
*------------------ end example ------------------

Hope this helps,
Maarten

--------------------------
Maarten L. Buis
Institut fuer Soziologie
Universitaet Tuebingen
Wilhelmstrasse 36
72074 Tuebingen
Germany

http://www.maartenbuis.nl
--------------------------

*
*   For searches and help try:
*   http://www.stata.com/help.cgi?search
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/

*
*   For searches and help try:
*   http://www.stata.com/help.cgi?search
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/
```