st: RE: How do I create a calendar year variable by person id before reshaping to person-year dataset?

[Holly E Reed <Holly.Reed@qc.cuny.edu>]

Thank you for your help, Maarten.  It worked great.  But now I am receiving error messages when I try to reshape the data.  No matter how I reshape, it tells me that the data are already in that format: "Data are already wide" or "Data are already long"  I have tried to do this several times, but with no luck yet.

This is my code:

reshape wide birth, i(id) j(year)

birth is a variable with suffix 1-10 (e.g., birth1, birth2, birth3, etc.) which is the year of a woman's first birth, second birth etc.

Sometimes the error message says "variable year not found"; I thought that year was a new variable that would be created? And once it said "i=id does not uniquely identify the observations; there are multiple observations with the same value of id." But I thought that was the point!?

If you can shed some light on these issues, I would appreciate it!
Thanks, Holly
_____________________________________

by id : gen year = birthyear + _n -1

also look at -help stsplit- as that command is there for creating such datasets.

Hope this helps,
Maarten
__________________________________________
Does the age of the person increase each year?

If so, you could use:
gen year = age+birthyear

If age does not increase each year, how do you know which year an
observation belongs to?
For example, how do you know the records aren't sorted like this:

id     age    sex    birthyear    year
1       5        F       1995        1999
1       5        F       1995        1998
1       5        F       1995        1997
1       5        F       1995        1996
1       5        F       1995        1995


Mike

_______________________________________
From: Holly E Reed
Sent: Wednesday, February 05, 2014 12:03 PM
To: statalist@hsphsun2.harvard.edu
Subject: How do I create a calendar year variable by person id before reshaping to person-year dataset?

Hi,

I am trying to create a person-year dataset for event history analysis. The dataset currently has one observation per person per year of their life, e.g.:

id     age    sex    birthyear
1       5        F       1995
1       5        F       1995
1       5        F       1995
1       5        F       1995
1       5        F       1995
2       3        M      1997
2       3        M      1997
2       3        M      1997

So person with id==1 is a 5-year old female born in 1995 and person with id==2 is a 3-year old male born in 1997. This is a simplified example to illustrate the dataset, as they are all adults and there are far more observations for each individual.

The problem is that I have age and birthyear variables, but I want to create a calendar year variable before reshaping the data to person-year data.  What is the easiest way to do this?  In other words, I want the dataset to look like this:

id     age    sex    birthyear    year
1       5        F       1995        1995
1       5        F       1995        1996
1       5        F       1995        1997
1       5        F       1995        1998
1       5        F       1995        1999
2       3        M      1997        1997
2       3        M      1997        1998
2       3        M      1997        1999

Thank you very much for any help you can give me!
Holly

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