Draw a random integer from the interval (a,b) but not c

[William Rossi]

Dear community,

I am trying to draw a random integer from an interval (a,b) but not c.
c obviously is inside the interval.

Specifically, I have a group of 20 individuals, and I selected an individual (say individual 5).
I need the function to randomly select a new individual in the group.

gen player = .
replace player = 1 if individual_counter == 5

replace player = 2 if individual_counter == runiformint(1,20) // and here I want to exclude the possibility of having 5 chosen

Thank you!

[Andrew Musau]

Here is a program that will do just that. You specify -lower limit, upper limit, to exclude- in the syntax.

capture program drop select
program define select, rclass
args a b c val
if `b'<=`a'{
    display as error "the upper limit must exceed the lower limit"
    exit
}
forval i=1/5{
    local val= runiformint(`1', `2')
    if `val'!=`3'{
        display "`val'"
        continue, break
    }
}
end

*TEST1
select 1 10 5

*TEST2
select 12 1 3

Res.:

. *TEST1
.
. select 1 10 5
6
 
.
. *TEST2

.
. select 12 1 3
the upper limit must exceed the lower limit

[Bruce Weaver]

Here's another approach (probably less flexible) approach that looks like works for the specific situation described in #1.

clear
set obs 20
generate byte individual_counter = _n
generate player = 1 if individual_counter==5
set seed 230908 // Change the seed value if you like

local ui = 5
while `ui'==5 {
    local ui = floor((20-1+1)*runiform() + 1)
    display "ui = " `ui'
}
replace player = 2 if individual_counter==`ui'
list if !missing(player), clean

/* References

https://blog.stata.com/2012/07/18/using-statas-random-number-generators-part-1/
https://www.stata.com/manuals/pwhile.pdf#pwhile

*/

Output:

. list if !missing(player), clean

       indivi~r   player  
  5.          5        1  
  9.          9        2

[William Rossi]

Thank you