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

# RE: st: RE: creating an index variable: number of presentations to hospital by participant

 From Nick Cox <[email protected]> To "'[email protected]'" <[email protected]> Subject RE: st: RE: creating an index variable: number of presentations to hospital by participant Date Thu, 28 Oct 2010 10:54:06 +0100

```That is,

bysort patient_id year (arrivaldate): gen order_in_year = _n

A tutorial on -by:- is included within

SJ-2-1  pr0004  . . . . . . . . . . Speaking Stata:  How to move step by: step
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  N. J. Cox
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

which is accessible to all via the Stata Journal website. I got the above text (and other hits) within Stata by

. search by, sj

-- and if you do that yourself you will get a clickable link to the corresponding .pdf.

Nick
[email protected]

Mitch Abdon

You may add the year variable in the -by- prefix. You need to include
the year variable in the -sort- as well. See "help by".

Alison McCarthy

> regarding the formula below. Is there a way to also split this up by year of presentation?
> This means you have the number of ordered presentations for each participant calculated separately for each year.

Kieran McCaul

>> You'll need some sort of patient ID that identifies individuals.
>> Assuming you have that, then:
>>
>> sort patient_id arrivaldate, stable
>> by patient_id: gen order=_n
>>
>>
>> look at -help sort- for an explanation of the option -stable-.
>>
>> Without this option, sort will randomly order observations with the same
>> patient_id and arrivaldate.
>>
>> Of course, if you have the arrival time as well, you could sort on:
>>
>> sort patient_id arrivaldate arrivaltime, stable

Alison McCarthy

>> I am working with a large data file containing presentations to a
>> hospital emergency department (ED). A number of individuals make more
>> than one presentation, which I have seen via the command 'duplicate'.
>> The organisation of my data is below:
>>
>> ARRIVALDATE repeaters part_ID age DISCHARGEDATE
>> 30-Mar-10 0 70 50 30-Mar-10
>> 30-Mar-10 0 70 50 30-Mar-10
>> 31-Mar-10 0 70 50 31-Mar-10
>> 01-Apr-10 0 70 50 01-Apr-10
>>
>> As can be seen, this person presented twice to the ED on the one day;
>> the second person presenting twice in a two-day period.
>>
>> I wish to create a new variable which tells me the number and order (in
>> terms of date) of presentations for each participant, and would greatly
>> appreciate some guidance.

*
*   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/
```

• Follow-Ups:
• References: