Dear Statlists,

I am currently working on an event study with a focus on the acquirers stock price reactions to a merger announcement as part of my thesis. I use the latest Stata Version 16.

The problem I am facing is that I have a list of different companies with their stock prices for periods 2013 to 2019 which are ordered in different columns (see example below)
Date A B C
01/01/2018 1 4 7
02/01/2018 2 5 8
03/01/2018 3 6 9






Due to my current programming in stata and according to the example event study by Princeton, I want my data table to look like this:
ID Date Price
A 01/01/2018 1
A 02/01/2018 2
A 03/01/2018 3
B 01/01/2018 4
B 02/01/2018 5
B 03/01/2018 6
C 01/01/2018 7
C 02/01/2018 8
C 03/01/2018 9

I would very much appreciate your help to quickly automize the rearrangement of my data to continue with my research.

BR Luka