topic Re: How to attribute a value of a given variable of a case to its matched control in All Things Community

How to attribute a value of a given variable of a case to its matched control

arzon — Thu, 12 Oct 2017 17:12:24 GMT

Hi dear,

I will be grateful if someone can help me with the following query:

I have cases matched to controls and I need to attribute a value of a case for a given variable to the corresponding matched control. as detailed in the tables below, I need to attribute the value "1" of the "Varx' of the case to the control (case=0) so that the value of the control for varx become 1 instead of missing.

Input table;

ID Macth_ID case Varx

1 1a 1 1

2 1a 0 .

Output expected:

ID Macth_ID case Varx

1 1a 1 1

2 1a 0 1

Thanks in advance for your support.

Re: How to attribute a value of a given variable of a case to its matched control

ballardw — Thu, 12 Oct 2017 17:28:11 GMT

Are you implying that your are matching on the Match_ID variable? If so, do you ever have more than two records with the same Match_id? Do you only have one non-missing value for Varx per Match_id?

Re: How to attribute a value of a given variable of a case to its matched control

arzon — Thu, 12 Oct 2017 17:46:58 GMT

Hi Ballardw

thanks for replying.

The data are already matched using the match_ID variable that identifies matched case and controls. Each case can have more than one control. Varx (that takes value 0 or 1) is missing for all the controls in the dataset but for each matched control the value of Varx is the same as for the case (i.e., if Varx =0 for the case, it should also be 0 for the matched controls).

Hope this clarify.

thanks again

Re: How to attribute a value of a given variable of a case to its matched control

Reeza — Thu, 12 Oct 2017 19:04:15 GMT

This is a lookup or merge.

You can use a data step merge or SQL, and the COALESCE() function is helpful.

Examples and explanations can be found here:

http://documentation.sas.com/?docsetId=lrcon&docsetTarget=n1tgk0uanvisvon1r26lc036k0w7.htm&docsetVersion=9.4&locale=en#p1dou269qdd63qn1pwvy421uk3vl

Re: How to attribute a value of a given variable of a case to its matched control

arzon — Fri, 13 Oct 2017 20:21:39 GMT

Thank you reeza for your suggestion and the link you shared. It was helpful.

Have a nice weekend!

Re: How to attribute a value of a given variable of a case to its matched control

AnnaBrown — Mon, 16 Oct 2017 14:00:25 GMT

Hi arzon,

I'm glad you found some useful info! If one of the replies was the exact solution to your problem, can you "Accept it as a solution"? Or if one was particularly helpful, feel free to "Like" it. This will help other community members who may run into the same issue know what worked.

Thanks!
Anna