How to create percentages?

[Daniel Abraham]

* Example generated by -dataex-. To install: ssc install dataex
clear
input long customer_id float platform
      35 1
      35 1
10794785 3
12407667 3
      35 1
      35 1
      35 1
      35 1
      35 1
 6834617 2
      35 1
 7280359 2
      35 1
10893468 2
 1747974 2
12093434 4
      35 1
 9821471 3
      35 1
 2676426 3
      35 1
      35 1
      35 1
      35 1
      35 1
      35 1
      35 1
 8139630 4
      35 1
      35 1
12562025 3
      35 1
11295091 2
13108472 2
      35 1
      35 1
 9369267 3
      35 1
11268838 2
 6344472 2
      35 1
      35 1
 7123191 2
11725152 2
 4959683 2
      35 1
      35 1
      35 1
11462866 2
 2730348 3
      35 1
      35 1
      35 1
11872647 2
 9930565 4
      35 1
      35 1
 8404195 3
      35 1
      35 1
 9930565 4
      35 1
      35 1
      35 1
      35 1
      35 1
      35 1
      35 1
 1438304 2
      35 1
      35 1
      35 1
 9930565 4
 5490563 3
      35 1
 5454891 2
 3200165 4
10484546 2
11274718 2
      35 1
      35 1
      35 1
 9930565 4
10038218 3
      35 1
 9369267 3
      35 1
 4621500 3
      35 1
 5863677 2
      35 1
      35 1
      35 1
 9930565 4
11040634 3
      35 1
      35 1
      35 1
      35 1
      35 1
end

The variable customer_id represents unique customer id. The variable platform represents the platform through which an customer ordered food. I would like to create a variable which shows the percentage of orders through platform 1 with respect to customer_id. If the customer has not ordered through platform 1, then 0. How should I proceed to create the new variable?

[Øyvind Snilsberg]

egen wanted = mean((platform==1) * 100), by(customer_id)

[Daniel Abraham]

Thanks! It worked