stack/unstack?

[River Huang]

Dear All, Suppose that I use -stack- command in the following.

 webuse stackxmpl, clear

. list

     +---------------+
     | a   b   c   d |
     |---------------|
  1. | 1   2   3   4 |
  2. | 5   6   7   8 |
     +---------------+

.         
. stack a b c d, into(e f) clear

. list

     +----------------+
     | _stack   e   f |
     |----------------|
  1. |      1   1   2 |
  2. |      1   5   6 |
  3. |      2   3   4 |
  4. |      2   7   8 |
     +----------------+

My question is: how can go from the bottom table to the top table? Thanks.

[Wouter Wakker]

webuse stackxmpl, clear
stack a b c d, into(e f) clear
bysort _stack: gen i = _n
reshape wide e f, i(i) j(_stack)
list

     +-----------------------+
     | i   e1   f1   e2   f2 |
     |-----------------------|
  1. | 1    1    2    3    4 |
  2. | 2    5    6    7    8 |
     +-----------------------+

drop i
rename * (a b c d)
list

     +---------------+
     | a   b   c   d |
     |---------------|
  1. | 1   2   3   4 |
  2. | 5   6   7   8 |
     +---------------+

[River Huang]

Dear Wouter, Many thanks for this helpful suggestion.