st: i-1 in forvalues loop

[Viktor Emonds <Viktor.Emonds@soc.kuleuven.be>]

Hey,

I am trying to draw a sample with random start, fixed interval systematic sampling procedure in each explicit stratum. The data in each stratum are already sorted by all the implicit stratifiers with serpentine sorting for a variable of particular interest. Now I just need to do the actual sampling and tried to start by doing the following:

use ethnicframe31                                                              //the specific explicit stratum
gen lotto=sum(studentsj3)                                                  //sum of target population
egen bal1= mean(3166.4667*runiform())                             //random starting point
forvalues i=2/15 {                                                          //Draw ' lotto balls' by adding the fixed interval
gen bal`i'= bal`i-1'*3166.4667
}

gen winnaar=0                                                                 //Identify ' winning'  schools
forvalues i=1/15{
replace winnaar=1 if inrange(bal`i',lotto[_n-1],lotto)
}

Apparently, the `i-1'  in the first loop is not understood. What am I doing wrong here? Thanks in advance!
Best,
Viktor
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