* do-file for Supplementary Exercise 3.40 of IPS7e,
* showing code for the third method described in the solution
version 15 /* works also with versions 13-14 */

import delimited "R:\Chapter 3\ex03_040.csv" 
sort excw
egen block=seq(), from(1) to (5) block(4)
set seed 140906
gen random=uniform()
sort block random
egen tx=seq(), from(1) to (4)
label define txgroup 1 "A" 2 "B" 3 "C" 4 "D"
label values tx txgroup
list, sepby(block)