[R] Egen and concat

David Winsemius dwinsemius at comcast.net
Thu May 30 07:15:33 CEST 2013

On May 29, 2013, at 3:10 PM, Daniel Tucker wrote:

> Let me explain what I am planning on doing; some background is  
> probably
> necessary and in hindsight the first email doesn't accurately  
> describe what
> I am looking to do. I'm trying to run a conditional logit model, but  
> I want
> to have a different strata depending on the value of another variable
> if sample==1 I want my strata to be stratida
> if sample==2 I want my strata to be stratidb
> if sample==3 I want my strata to be stratidc
> stratida/stratidb/stratidc are NOT variables already in the dataset.
> they represent a string combination of three already present numerical
> variables (year, byregn2, group) and differ for when the variable  
> sample is
> ==1,2 or 3. They are different variables for labeling purposes. What  
> I am
> looking to do is replicate these in one variable--make one variable  
> that is
> the string combination of year, byregn2, and group and then use it  
> as my
> strata.

If dfrm is a data.frame with column names: year, byregn2, group then  
creating a 4th column named strata:

     dfrm$strata <- with( dfrm, paste0(year, byregn2, group) )

If you want tested code, you need to offer actual R objects.

> On Wed, May 29, 2013 at 1:53 PM, Adams, Jean <jvadams at usgs.gov> wrote:
>> You are limiting yourself to getting help from only those people that
>> understand the STATA language.  You may improve your chances for a  
>> helpful
>> response if you tell us in English what the STATA commands mean.
>> Jean
>> On Wed, May 29, 2013 at 10:37 AM, Daniel Tucker <dtucker9 at u.rochester.edu 
>> >wrote:
>>> R list members,
>>> I am trying to replicate a command script in STATA and find
>>> equivalency in R to the following Stata command:
>>> egen stratida = concat(year byregn2 group) if sample==1
>>> egen stratidb = concat(year byregn2 group) if sample==2
>>> egen stratidc = concat(year byregn2 group) if sample==3
>>> Not sure if I should just try to make a for loop and use the paste
>>> operator or if there is somewhere else I should be looking.
>>> Thanks,
>>> Daniel

David Winsemius, MD
Alameda, CA, USA

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