Dropping a duplicate in variable 1 if it was also different in variable 2

[heba nayel]

Hello,
I am new to stata and need help in the following :

Variable 1 ( ID)	Variable 2 (color)
1	red
1	red
2	blue
2	green
3	purple
4	red

Example :
Within duplicates of ID , I want to drop the IDs where the duplicates are different in color but keep IDs that have duplicates with the same color .
i.e.
I want to drop both duplicates with ID 2 because one is blue and the other is green
I want to keep duplicates for ID 1 because both duplicates have red color
Thank you !

[Carlo Lazzaro]

Heba:
welcome to this forum.
As a bit of surgery at this end since you forgot to use -dataex- to share your data excerpt/example, you may want to try:

. egen wanted=group( Var_A Var_B)

. list

     +-------------------------+
     | Var_A    Var_B   wanted |
     |-------------------------|
  1. |     1      red        1 |
  2. |     1      red        1 |
  3. |     2     blue        2 |
  4. |     2    green        3 |
  5. |     3   purple        4 |
     |-------------------------|
  6. |     4      red        5 |
     +-------------------------+

. bysort Var_A: drop if wanted[_n]!=wanted[_N]
(1 observation deleted)

. list

     +-------------------------+
     | Var_A    Var_B   wanted |
     |-------------------------|
  1. |     1      red        1 |
  2. |     1      red        1 |
  3. |     2    green        3 |
  4. |     3   purple        4 |
  5. |     4      red        5 |
     +-------------------------+

.

[Carlo Lazzaro]

Heba:
if you want to -drop- the whole panel for which the condition is satisfied:

bysort Var_A: drop if wanted[_N]!=wanted[_N-1] &_N==2
(2 observations deleted)

. list

     +-------------------------+
     | Var_A    Var_B   wanted |
     |-------------------------|
  1. |     1      red        1 |
  2. |     1      red        1 |
  3. |     3   purple        4 |
  4. |     4      red        5 |
     +-------------------------+

.

[heba nayel]

Thank you very much Carlo !
This was very helpful.