[R] Equivalent to Stata egen tag

Denis Kazakevich den2042 at yahoo.com
Sun Jan 23 20:07:56 CET 2011

Dear David
Thank you for your e-mail
I believe that  equivalent to Stata egen tag is simply

df$tag <- df[!duplicated(df[c("station","week")]),]

I am not sure about 
egen count 

It might be something like
aggregate(station~week, df, function(x)sum(!is.na(x)), na.action = na.pass)

I made this question while making very first steps in R after actively using 
Stata for 3 years. And I underestimated  the extent of flexibility of R. But 
after your answer on one of my previous questions I realized that I can  use, 
for instance mean(tapply(<sth>)) or table(<sth>)/<sth> right away which is great 

With best regards

----- Original Message ----
From: David Winsemius <dwinsemius at comcast.net>
To: Denis Kazakevich <den2042 at yahoo.com>
Sent: Sun, 23 January, 2011 17:56:53
Subject: Re: [R]  Equivalent to Stata egen tag

On Jan 16, 2011, at 6:48 PM, Denis Kazakevich wrote:

> What are the R equivalents to the Stata command egen tag
> and
> egen count?
> egen station_week_tag = tag(station week)

I have looked at similar questions in the past and gone to the Stata online docs 
and tried to make some sense of them and even posted an attempt at an answer. 
The documents appeared to be to be fairly cryptic. Much more so that the R 
documentation. I was somewhat snottily informed by experienced Stata users that 
I had completely misunderstood the documentation and that egen was much more 
rich an varied that I understood. So I've given answering Stata questions. Given 
the protean nature of the egen I think it's unrealistic of you to expect that 
just posting code will communicate what you intended.

David Winsemius, MD
Heritage Laboratories
West Hartford, CT

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