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From |
"Haardt, David A M" <damhaa@essex.ac.uk> |

To |
<statalist@hsphsun2.harvard.edu> |

Subject |
st: Multiple spells: -ltable- to graph hazards by age rather than by duration? |

Date |
Fri, 18 Jun 2004 14:37:35 +0100 |

Dear Statalisters, I have a dataset where each row corresponds to one labour-market spell of a particular person. Among the variables are person ID, spell start date, spell end date, labour market-status, interview date, and date of birth. I use these variables to generate age at spell start date (ageatbeg) and age at spell end date (ageatend). The data are recorded in monthly intervals. Is there any way of using the -ltable- command (or any other existing command) to graph hazards by age rather than by duration? I don't want to stratify the hazards by age group, but rather have age itself on the abscissa to be able to see whether certain labour-market transitions occur mainly at certain key ages. As far as I can see I get erroneous results with -ltable- since in the logic of this command a failure time of 780 (ie, a certain labour-market transition at exact age 65, since 780/12=65) implies that the person was at risk for 65 years, which is of course not correct. In mortality studies, the distinction between age and duration does not matter since you can only die once, but in my case it does matter. In other words, my problem seems to be caused by the multiple spell structure, which implies that age!=duration+x since people have different numbers of spells of different lengths. I know what I would like to do in terms of simple Stata commands: sort pid ageatbeg count if ageatbeg<780 & ageatend>=780 & ageatend!=. & status==1 returns the number of people in status "1" at exact age 65, therefore my risk set, and count if ageatend==780 & status==1 & status[_n+1]==3 & pid==pid[_n+1] then returns the number of people who have made a transition from status "1" to status "3" within the first month after exact age 65, therefore my failure set. The problem is that even if I use loops to calculate these numbers using the latter two command lines for each monthly age, there's no easy way of tabulating and/or exporting the data. My question therefore is whether there's any way of getting the calculations I want nicely tabulated, for instance reorganising my data somehow? I am of course aware of the option of modifying the ltable.ado file but maybe somebody else has already dealt with this or a similar problem so that I don't have to do that. I would be very grateful for any hint and appreciate your time and effort. Best regards, David -- Mr David A M Haardt <damhaa@essex.ac.uk> Institute for Social and Economic Research University of Essex, Colchester CO4 3SQ, UK Tel: +44 (0)1206 873569; Fax: +44 (0)1206 873151 <http://www.iser.essex.ac.uk/home/damhaa/> * * For searches and help try: * http://www.stata.com/support/faqs/res/findit.html * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

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