st: matching cases by a transitive relation

[Robert De Vries <robert.devries@sociology.ox.ac.uk>]

Dear Statalisters,

I have a problem with attempting to match cases by a transitive relation (A is related to B, B is related to C, so C must be related to A).

Specifically, I am working with the longitudinal British Household Panel Study (BHPS), and I am attempting to match siblings across time. I can straightforwardly create a dataset which includes the ID number of all sibling pairs in the dataset in the following format:

ID            |              SIBLING ID
A             |              B             
B             |              A
B             |              C

However, this dataset does not reflect the additional relationship A-C. This occurs when A and C are siblings but have never actually lived together. For example, in Wave 1, A and B are siblings living together. By Wave 2, A has moved out, and B has gained a new sibling; C (this might be a step-sibling, for example, or a new birth). My dataset reflects that fact that A and B are siblings, and that B and C are siblings, but because A and C have never been coded as siblings, my dataset does not reflect that they are. 

By their transitive relation through B, we know that A and C are siblings. My question is: what code could I write to get the dataset to reflect this? I need to somehow tell Stata that if A is related to B AND B is related to C, you need to create a new case which reflects that A is related to C.

Hope you can help!

Robert de Vries


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