Combining multiple observations with same unique ID into one observation

[Nikhil Kanakamedala]

Hello,

I want to combine multiple observations with same unique ID into a single observation and replace the missing values of the variables if the value exists in any of the duplicates.
I have tried to search in the forum, however most solutions offered work if there is 1 copy of duplicate based on ID. However, in my dataset the ID has multiple copies of duplicates and it is not a fixed number (copies = 0 to 9).

My current dataset looks like this

ID	var1	var2	var3	var4	var5
1	.	1	.	5	.
1	2	.	.	.	.
1	.	.	.	.	3
2	1	.	.	.	.
2	.	3	.	.	.
3	5	.	.	.	.
3	.	7	.	.	.
3	.	.	6	.	.
3	.	.	.	7	.

Required output is

ID	var1	var2	var3	var4	var5
1	2	1	.	5	3
2	1	3	.	.	.
3	5	7	6	7	.

[Carlo Lazzaro]

Nikhil:
welcome to this forum.
See -help collapse-.

[Nick Cox]

I agree with Carlo Lazzaro. The simplest collapse of all, using means, works with the data example.

Note the use here of dataex (FAQ Advice #12).

* Example generated by -dataex-. For more info, type help dataex
clear
input byte(id var1 var2 var3 var4 var5)
1 . 1 . 5 .
1 2 . . . .
1 . . . . 3
2 1 . . . .
2 . 3 . . .
3 5 . . . .
3 . 7 . . .
3 . . 6 . .
3 . . . 7 .
end

. collapse var? , by(id)

. l

     +---------------------------------------+
     | id   var1   var2   var3   var4   var5 |
     |---------------------------------------|
  1. |  1      2      1      .      5      3 |
  2. |  2      1      3      .      .      . |
  3. |  3      5      7      6      7      . |
     +---------------------------------------+

[Nikhil Kanakamedala]

Thank you Carlo Lazzaro and Nick Cox. Worked like a charm
Thanks also on the advice to use dataex. Will do from my next post.