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Re: st: specify groups within a group


From   Joseph Coveney <[email protected]>
To   Statalist <[email protected]>
Subject   Re: st: specify groups within a group
Date   Fri, 08 Dec 2006 16:30:33 +0900

Lucy Shum wrote:

Hi all, could anybody advise on how to specify in STATA, analysis of
specific groups within a category? That is, if I have a category called
events_mastitis - there are 7 different groups meaning there are animals
that experienced between 1 - 7 episodes of mastitis within a lactation. Say
if I only want STATA to analyze, tabulate, create graphs of.., say Group 1
and 5 only. How do I go about doing that?

Also, using the example above, how do I go about writing a command so that
STATA compares the survival estimates of these 7 groups? Logrank? Is there a
modified procedure that deals with comparison of greater than 2 groups?

--------------------------------------------------------------------------------

You can use -inlist()- to select groups:

tabulate pathogen if inlist(events_mastitis, 1, 5)

You can use Stata's survival commands for comparing more than two groups.
The example below creates four groups (age categories) and peforms a
log-rank test and Cox regression.

Joseph Coveney

use http://www.stata-press.com/data/r9/catheter, clear
bysort patient (time): keep if _n == _N
egen byte age_category = cut(age), group(4)
stset time, failure(infect)
sts test age_category
xi: stcox i.age_category
exit


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