st: identifying the unique values across variables and creating new var equal to them

["Ivanova, K.O." <K.O.Ivanova@uva.nl>]

Dear all,

I have a dataset where each row corresponds to a couple. Each partner within a couple was asked to report the birthdates of his / her children (not specified whether own or step). I need to find a way to identify the cases when one partner reported a birthdate which the other partner did not (this is the only way for me to identify children born outside the current union).

This is my data structure (the values are fictional, in my data the values as coded as century month codes; the variables starting with "par_" are based on the answers of the partner of the respondent):

id	ch1	ch2	ch3		par_ch1	par_ch2	par_ch3

1	3	9	12		7		9		12	

2	2	5	3		.		.		.

3	9	11	7		7		4		11

And I need to find a way, based on the data above, to create the following new variables (with their corresponding, for this example, values):

id	ex1	ex2	ex3	par_ex1 	par_ex2	par_ex3

1	3	.	.	7		.		.

2	2	5	3	.		.		.

3	9	.	.	.		4		.

Basically, I need to find a way to check the value of each birthdate against the rest of the birthdates reported *within* a couple. If that birthdate is reported by the other partner as well, the child is common and thus, of no interest for me. When the birthdate is unique within the couple, that child is a child only of the partner that reported it and the new variable should take the  value of that birthdate.

I hope the example is clear and would appreciate any help I can get.

Katya

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