Data ...; merge dataset1 (in=a) dataset2 (in=b) ...

[cdubs]

I'm trying to understand the following code: 

data final_eligibilityfile (drop=dtstart);
		merge eligibility_2 (in=a) status (in=b) county (in=c) ;
		by PID starting ending;
		if a;
run;

Two questions: 

- What is the purpose of (in=b) and (in=c) if we don't reference b or c later on in the code (?) (as far as I'm aware)

- What does the "if a" mean? Does that mean if a given variable is in a (e.g. "eligibility_2")? 

Thank you!

[WarrenKuhfeld · Accepted solution]

in= variable creates a binary variable that tells you if that input data set contributes to this observation.  Correct--if you don't use them, there is no point in making them.

The IF statement is a subsetting IF.  If the variable is true (1 in this case) processing is continued and the observation is output.

The code is keeping all observations that come at least in part from the eligibility_2 data set.

[Reeza]

IN= Data Set Option

Creates a Boolean variable that indicates whether the data set contributed data to the current observation.

https://support.sas.com/documentation/cdl/en/ledsoptsref/69751/HTML/default/viewer.htm#n1p1o2dsuc465...

[ballardw]

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@cdubs wrote:

I'm trying to understand the following code: 

data final_eligibilityfile (drop=dtstart);
		merge eligibility_2 (in=a) status (in=b) county (in=c) ;
		by PID starting ending;
		if a;
run;

Two questions: 

- What is the purpose of (in=b) and (in=c) if we don't reference b or c later on in the code (?) (as far as I'm aware)

- What does the "if a" mean? Does that mean if a given variable is in a (e.g. "eligibility_2")? 

Thank you!

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Perhaps you should investigate the free online courses and tutorials at https://support.sas.com/edu/elearning.html?ctry=us&productType=library