Reshape Panel Data Wide Format to Long Format
问题 I am struggling with transformation of a Panel Dataset from wide to long format. The Dataset looks like this: ID | KP1_430a | KP1_430b | KP1_430c | KP2_430a | KP2_430b | KP2_430c | KP1_1500a | ... 1 .... 2 .... KP1; KP2 up to KP7 describe the Waves. a,b up to f describe a specific Item. (E.g. left to right right placement of Party a) I would like to have this data in long format. Like this: ID | Party | Wave | 430 | 1500 1 1 1 .. .. 1 2 1 .. .. . . . 1 1 2 .. .. . . . 2 1 1 .. .. I tried to