Extract entries across rows?

[lianlian]

Dear Statalist,

Imagin 3 players transmitting messages, we say a player transmits a message correctly if she copied the same message with her upstream player.
Now I have the data of all the copied messages and the sequence of players but I don't know how to create the new variable recording whether she copied the upstream message correctly.
i.e. whether the message she copied is the same as her upstream message.

    input id entry1 entry2 entry3
    1  123 456 789
    2  789 123 456
    3  456 789 123
    end

I want to generate a new variable say whether entry2 is copied correctly. If player2's entry 2 = player1's entry1, we say player2 copied correctly.
Something like the following (which is not working "invalid syntax"):

bysort id: gen correct2=1 if id==2 & entry2[2]==entry1[1]

Any help would be much appreciated!

[Andrew Musau]

* Example generated by -dataex-. For more info, type help dataex
clear
input float(id entry1 entry2 entry3)
1 123 456 789
2 789 123 456
3 456 789 123
end

sort id
gen wanted= entry2== entry1[_n-1] & entry3== entry2[_n-1]

Res.:

. gen wanted= entry2== entry1[_n-1] & entry3== entry2[_n-1]

. l

     +----------------------------------------+
     | id   entry1   entry2   entry3   wanted |
     |----------------------------------------|
  1. |  1      123      456      789        0 |
  2. |  2      789      123      456        1 |
  3. |  3      456      789      123        1 |
     +----------------------------------------+

[lianlian]

Many many thanks! Andrew!