I want to create lead and lag values by group and conditional on another columns
I want to create lead and lag variables for column 'Value', the 'Value_lead1' only exists when year difference is 1, otherwise it equals NaN. Also, the 'Value_lag1' only exists when year difference is 1, otherwise it equals NaN.
| Group | Year | Value | Value_lead1 | Value_lag1 |
|---|---|---|---|---|
| A | 1993 | 1 | 2 | NaN |
| A | 1994 | 2 | NaN | 1 |
| A | 1996 | 3 | 4 | NaN |
| A | 1997 | 4 | NaN | 3 |
| B | 1992 | 1 | NaN | NaN |
| B | 1997 | 2 | 3 | NaN |
| B | 1998 | 3 | 4 | 2 |
| B | 1999 | 4 | NaN | 3 |
