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Re: st: Need help converting values into factor variable


From   Nick Cox <njcoxstata@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Need help converting values into factor variable
Date   Sat, 1 Dec 2012 12:53:53 +0000

sum()     create running sum (see -help sum()-)

year != year[_n-1]     year not equal to previous year
     expression evaluated as 1 if true and 0 if false

see
FAQ     . . . . . . . . . . . . . . . . . . . . . . .  True and false in Stata
        . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  N. J. Cox
        2/03    What is true and false in Stata?
http://www.stata.com/support/faqs/data-management/true-and-false/

This works also for the _first_ observation for each patient as the
previous year is then evaluated as missing (which is fine; missing is
not any of 2009 ... 2012)

inrange(year, 2009, 2012)    year in range 2009 to 2012 (may be
superfluous if you _don't_ have other years -- but you did not say
that)

Nick

On Sat, Dec 1, 2012 at 12:44 PM, Michael Stewart
<michaelstewartresearch@gmail.com> wrote:

> I am trying to decipher the code written by you(sort, I am by no means
> and stata expert )
> Can you explain what this code is doing; especially the argument (
> sum(year != year[_n-1] &
>> inrange(year, 2009, 2012))

On Sat, Dec 1, 2012 at 7:17 AM, Nick Cox <njcoxstata@gmail.com> wrote:

>> This is not "Statlist"!
>>
>> You should show us your code that you tried to get an explanation of
>> what you are getting wrong.
>>
>> bysort patient (year) : gen flag = sum(year != year[_n-1] &
>> inrange(year, 2009, 2012))
>> by patient : replace flag = flag[_N]
>>
>> Nick
>>
>> On Sat, Dec 1, 2012 at 11:55 AM, Michael Stewart
>> <michaelstewartresearch@gmail.com> wrote:
>>
>>> Dear Statlist reader ,
>>> I am having trouble converting  my values into factor variables and am
>>> looking for help. My data looks as follows where "patientid" is pt
>>> identification number and "year_elevated" is year in which a
>>> particular lab value was elevated
>>>
>>>
>>> patientid       year_elevated
>>> 111             2009
>>> 111             2009
>>> 222             2009
>>> 222             2011
>>> 222             2012
>>> 333             2009
>>> 333             2012
>>> 444             2011
>>> 444             2012
>>> 555             2009
>>> 555             2010
>>> 555             2011
>>> 555             2012
>>>
>>> I want to create a factor variable (y  )with values 1= ,2 , 3 and 4
>>> where  for each distinct patientid
>>> y=1 if year_elevated  has anyone of ( 2009 or 2010 or 2011 or 2012)  values
>>> y=2 if year_elevated  has  any two of ( 2009 , 2010 , 2011 ,  2012)  values
>>> y=3 if year_elevated has  any three of ( 2009 , 2010 , 2011 ,  2012)  values
>>> y=4 if year_elevated  has  all four of ( 2009 , 2010 , 2011 ,  2012) values
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