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st: RE: gen new variable, dealing with prefix codes


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: RE: gen new variable, dealing with prefix codes
Date   Tue, 27 Jun 2006 21:57:40 +0100

Many listers get flak for vague, circuitous or otherwise
unanswerable questions. This is a model of clarity! 

I guess that when you say "byte" you mean "digit". 
I also note that if this is the case then nobody dies at age
100 or above. 

I will call your variable -ndeath-. 

It will be convenient to convert this to a string by

gen sdeath = string(ndeath) 

Death in years is given by 

gen ydeath = real(substr(sdeath,2,.)) if substr(sdeath,1,1) == "1"

which will be missing for deaths below 1 year. 

Death in months is given by 

gen mdeath = real(substr(sdeath,2,.)) if substr(sdeath,1,1) == "2" 

which will be missing for deaths at or above 1 year or below 1 month.

Death in days is given by 

gen mdeath = real(substr(sdeath,2,.)) if substr(sdeath,1,1) == "3" 

which will be missing for deaths at or above 1 month. 

And so on. 

Those might be useful for later applications. For example, 
you might want a combined variable which could be 

gen death = cond(ydeath < ., ydeath, 0) + cond(mdeath < ., mdeath/12, 0) 
			+ cond(ddeath < . , ddeath / 365.25, 0) 

with extra terms for the other variables. 

Your classification is 

gen myclass = 1 if substr(sdeath,1,1) != "1" 
replace myclass = 2 if ndeath < 5 
replace myclass = 3 if ndeath < 15 & missing(myclass) 

and other commands like the last. 

And the moral is: 

        The functions are your friends. 
	  Browse in the help for -functions-. 

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

LaVera Crawley
 
> I am working with a 3 byte numeric variable of age at death where the 
> first integer (prefix) codes whether the next 2 integers are in 
> years, months, days, hours, or minutes. So it lists age in years 
> as  1 + years; It lists months as 2 + months; days are  3 + days 
> etc.  For example, a person who died at 59 years of age is coded as 
> 159; a child who died at 3 months of age is coded as 203; death at 4 
> days is 304; death 6 hours after birth is 406; etc.
> 
> I need to convert this to the following 11 age intervals in years:
> 0 to less than 1;
> 1 to 4;
> 5 to 14;
> 15 to 24;
> 25 to 34;
> continuing 10 year intervals up to 85+.
> 
> I am having trouble creating a stata command for this because of how 
> the bytes are set up (because of the prefix month, day, hour, & 
> minute integers.)  Please help!

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