st: re: data creation for hazard regression

[Kenisha Russell <kenisha.russell@framtidsstudier.se>]

Hi Statalisters,
I am trying to create a data set for which I will use  hazard regression (events history analysis to demographers).
I am currently restructuring my data into person-period format, in order to use hazard regression to examine the propensity of an individual to transition from state x to state y.
and one of the variables that I want to use is pregnancy.

Because I have the day and month each child was born, after making this date into century month format, I have simply subtracted the 7 months previous to the birth of each child to obtain   a variable called pregnancy. In this particular data set the highest recorded parity is 3. See the syntax I have used below.

gen CMpregnancy1=.
replace CMpregnancy1=CMchild1-7 if CMchild1!=999999
CMchild is the birthdate of the each child is in century month format.


After this I then split the data: 
stsplit pregnancy1, after(CMpregnancy1) at(0)

/* We replace values for pregnancy1 so that 0 represents time before that 
the woman was pregnant and 1 for after the pregnancy*/
replace pregnancy1= pregnancy1+1
replace pregnancy1=0 if CMpregnancy1==.
list  pid-_st CMpregnancy*  pregnancy* in 1/60

This is repeated three times because given the fact that highest parity is = 3,  the likelihood of pregnancy is also 3 and all should be taken into account.

Although I have written a syntax here and have split the data, my issue is that I am not sure it is correct. Am I required to split the data with each pregnancy?  i.e to create a time = before the event (i.e the pregnancy).

 If I do split the event, if my reasoning is correct I assume I would need to stop each pregnancy at the point where each child is born.  Is that correct? If so, How would I do that?

Best,
Kenisha



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