How to Merge by Minimum Number of Observations in By Group?

[jlajla]

If I'm mot mistake, merge will, by default, make the total number of observations in the final data set set as the sum of the maximum number of observations in a BY-group from either data set.

How do I make the total number of observations in the final data set as the sum of the MINIMUM number of observations in the BY group from either data set?

I have this:

ID region

1  A

1 A

2  A

2 A

3  B

3 B

4  C

and

ID  size

1  5

1  6

1  7

2  3

2  4

3  4

3  5

4  5

& I'd like:

ID region size

1 A 5

1 A 6

2 A 3

2 A 4

3 B 4

3 B 5

4 C 5

Thank you in advance. 

[LinusH]

How do you know that the first row in the "size" data set is the right one?

If you know, just use

if first.ID;

Assumng that there are no duplicates of ID in the "region" data set.

[jlajla]

Thank you.  I should elaborate.  My first data set is actually similar to this:

1 A

1 A

2 A

2 A

3 B

3 B

4 C

4 C

And I'd like to match by the number of observations in this dataset. However, if I use first.id, then it only matches by the very first observation.

[LinusH]

Perhaps you should share some real data, because this logic makes little sense.

Merging data without proper keys (unique by variables) leads to unpredictable results, and inconsistent data.

[Astounding · Accepted solution]

data minimum;

in1=0;

in2=0;

merge a (in=in1) b (in=in2);

by id;

if in1 and in2;

run;

[jlajla]

Perfect. If modified to "if in1" this gives the exact results I needed. Thank you!