Random group generation

[Cong Gu]

Dear Statalists,

I would like to generate 67 random groups for 271 observations. I know the below code might work:

set obs 271
range no 1 271
gen r= uniform()
gen group=1
sort r
replace group=2 in 5/8
...

However, is there any better way that can be used to generate 67 random groups simultaneously?

Thanks in advance.

Best,
Cong

[Clyde Schechter]

set obs 271
range no 1 271
set seed 1234 // OR YOUR FAVORITE SEED
gen r = uniform()
sort r
gen group = ceil(_n/4)
sort group no

Note: 271 != 67*4, so you will actually have 68 groups, with the last group having only 3 members. In fact, 271 is a prime number, so there is no possibility of dividing 271 observations into groups of exactly equal size. If you prefer to have only 67 groups, with the last group containing 7 members, just add -replace group = 67 if group == 68- at the end of the code shown above.

[Cong Gu]

Dear Clyde, many thanks for the reply. That is very helpful! Best, Cong