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st: RE: Loop question


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: RE: Loop question
Date   Fri, 28 Sep 2007 15:42:09 +0100

I take it the typical observation (case, record) is for 
a patient's visit and includes -arrdt- and -dcdt-. 

I think a loop may be needed _with this data structure_. 

gen already = . 
qui forval i = 1/`= _N' { 
	count if arrdt < arrdt[`i'] & dcdt > dcdt[`i'] 
	replace already = r(N) in `i' 
}

It is easier in a different data structure which 
has two observations for every patient visit. Then 
you create a score +1 for an arrival and -1 for a departure
and use -sum()- to get the number in the queue. 
Subtract 1 to get -already-. 

This different data structure could be got via
-reshape long-. 

Other questions about timing would I think 
always be easier in that data structure. 

-search count- to find a reference to Stata Journal tutorials on 
how useful -count- can be. 

Nick 
n.j.cox@durham.ac.uk 

Steve Pitts
 
> I'm trying to work out how many patients are already present 
> in an emergency 
> department (a variable called "how_busy") for each member in 
> a list of 
> patients that includes the variables "arrival datetime" and 
> "discharge 
> datetime", i.e. I'd like to know how many patients preceding 
> the index 
> patient have dcdt > current arrdt in a list of visits sorted 
> by arrdt.  I'm 
> no programmer and fairly new to Stata, and haven't been able 
> to make it work 
> using -forval- and -while- loops with explicit subscripting. 
> Maybe there's a 
> clever way to do this using -egen-?
> 
> An alternative "how_busy" measure might be a count of all 
> patients who were 
> in the ED during any part of the index patient's visit (maybe 
> it got busy 
> later). I think this would need to be divided by length of 
> stay. In any case 
> for me: equally impossible, but maybe this is easy for someone else.

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