RE: st: generating dummy variables based on freq of duplicate values

[Willard van Ooij <w.van.ooij@marktmonitor.com>]

I may be missing something, but isn't this solution much easier?

gen highfreq=0
bys patientid: replace highfreq=1 if _N>4

But this only works if Yerik want just 2 groups, a high and low frequency group.

Willard

-----Oorspronkelijk bericht-----
Van: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] Namens Eric A. Booth
Verzonden: dinsdag 20 augustus 2013 6:29
Aan: statalist@hsphsun2.harvard.edu
Onderwerp: Re: st: generating dummy variables based on freq of duplicate values

<>
Take a look at -help egen-, particularly the cut() function.  Here's one way to get what you are asking about:

********************!begin example
clear
set obs 500
g patientid = trunc(runiform()*50)

bys patientid: egen freq = count(patientid) su freq

egen freqcat = cut(freq), at(0 4 10 30) lab ta freqcat, miss

ta freqcat, g(cat_)

su cat_?
********************!end example

- Eric




On Mon, Aug 19, 2013 at 8:55 PM, Yerik Kaslow <yerik.kaslow@gmail.com> wrote:
> Hello Statalist,
>
> I apologize if this email already got sent out. I sent it w the word 
> help in the first line so it may have bounced, I am sorry if this is a 
> duplicate email. I'm not trying to spam the listserv, I'm just new at 
> this.
>
> I am working w a dataset for clinical trials. My data has patient IDs 
> which often repeat; everytime they participate in a trial, they are 
> recorded. I want to group the patient IDs into high frequency and low 
> frequency participants, based on the frequency they are involved with 
> the clinical trials. I am trying to write syntax to create a dummy 
> variable based on frequency of duplicate patientIDs.
>
> EG:
> Patient ID 6523 appears 2 times
> Patient ID 7634 appears 10 times
> Patient ID 8798 appears 4 times
> Patient ID 9032 appears 21 times
>
> I would like to write syntax such that any patient ID with a frequency 
> of <= 4 (or any other value I choose) is assigned value of 0...low 
> frequency patient in this case. Likewise, any patient ID with a 
> frequency of >=5 is assigned a value of 1...high frequency patient.
>
> How would I write syntax to say, assign a value of 1/0 based on the 
> number of the same patient IDs in the data?
>
> Thank you,
>
> Yerik
>
> --
> Yerik Kaslow
> yerik.kaslow@gmail.com
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