Generating a variable whose values are the total number of times a value exists in another variable

[Nabuu Shergill]

Hello to everyone,

I want to generate a new variable that is the sum of the number of times another variable takes on a certain value. I can use the "count if" command, and I know that the value 351 appears 211 times in my ID variable. So I want to create a new column that will have the value 211 every time ID is equal to 351. And I know the value of 355 appears 494 times in my ID column, so I want my new variable column to have the value of 494 every time ID is equal to 355.

So if my data was the below, I would want it to look like this:

ID:	newvar
355	3
351	2
356	1
355	3
358	1
359	2
351	2
357	1
355	3

Since 355 appears 3 times, the newvar variable takes on the value of "3" everytime ID is equal to 355. And since 351 appears twice, newvar takes on the value of 2 every time ID is equal to 351. Unfortunately my is data large, with over 1,250 observations. Any assistance would be greatly appreciated.

[Andrew Musau]

bys id: egen wanted=count(id) if !missing(id)

[Nabuu Shergill]

Oh wow. Andrew, thank you so much. I was not aware of the bysort function. This has been a great learning experience. Thank you again

[Nick Cox]

bysort id : gen wanted = _N

is another way to do it.