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Re: st: looking for more efficient programming for randomly shuffling list of numbers


From   Jeph Herrin <stata@spandrel.net>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: looking for more efficient programming for randomly shuffling list of numbers
Date   Fri, 27 Aug 2010 10:45:48 -0400

A more substantial point is that my solution doesn't generate
a list of 20 distinct integers - there can be repetitions in the
list. But here's a solution using -rowranks-

**************
ssc install rowranks
**************
  clear all
  set obs 9600
  set seed 85999283
  gen str60 sticker=""
  forv i=1/20 {
	gen num`i'=runiform()
  }
  rowranks num1-num20, gen(rank1-rank20)
  forv i=1/20 {
	replace sticker=sticker+" "+string(rank`i')
  }
  drop num1-num20 rank1-rank20
**************


On 8/27/2010 4:46 AM, Nick Cox wrote:
A very minor point, but -ceil(20* runiform())- is also a nice way to
get uniform integers 1 ... 20 (for "any value of 20").

Yet another posthumous nod to Kenneth E. Iverson, who came up with
the names floor and ceiling for the round up and down functions
yielding integer results.

Nick n.j.cox@durham.ac.uk

Jeph Herrin

How about

************** clear all set obs 9600 set seed 85999283 gen str60
sticker="" gen num=. forv i=1/20 { replace num=floor(20*uniform())+1
replace sticker=sticker+" "+string(num) } drop num **************

?

On 8/26/2010 11:11 AM, Evelyn Ersanilli wrote:

For a survey I need to make stickers that can be used to randomly
select respondents within a household. These stickers should
contain the numbers 1-20 in a random order (most households will
have less than 20 members). Each sticker should have its own random
order, though it is not a problem if by chance some stickers are
the same. The stickers should be generated in such a way that each
order of numbers 1-20 should be possible and equally likely.

I have written a do-file for this (see below), but it's pretty
inefficient. My first step was to make a data file with one
variable that has the numbers 1-20 (so 20 cases). Then I let the
do-file run to create 70 random lists of the numbers 1-20. The main
inefficiency is that I had to create a separate .dta file for each
sticker and then merge them. This is not so bad with 70 lists, but
with the 9.600 that I will need to create it is pretty annoying.

The recent discussion about need for setting the random seeds also
got me a bit worried, but if I understood it correctly it
shouldn't affect my problem too much.

All suggestions are welcome.

Kind regards,

Evelyn

****************************** local i = 1 while `i'<   71 {
//generates 70 vars with random numbers gen u`i' = runiform() local
i = `i' + 1 }

foreach order of varlist u1-u70 { sort `order' gen
order`order'=var1 preserve keep order`order' gen n=_n save
"C:\Users\sticker source`order'.dta" restore }

clear gen n=_n foreach order in u1 u2 u3 u4 u5 u6 u7 u8 u9 u10 u11
u12 u13 u14 u15 u16 u17 u18 u19 u20 u21 u22 u23 u24 u25 u26 u27
u28 /// u29 u30 u31 u32 u33 u34 u35 u36 u37 u38 u39 u40 u41 u42 u43
u44 u45 u46 u47 u48 u49 u50 u51 u52 u53 u54 u55 u56 u57 u58 u59 u60
/// u61 u62 u63 u64 u65 u66 u67 u68 u69 u70{ merge 1:1 _n using
"C:\Users\sticker source`order'.dta", noreport nogenerate } drop n
save "C:\Users\sticker pilot 1 marok.dta", replace xpose, clear
outsheet using "C:\Users\sticker pilot 1 marok - transposed.out",
replace ***************************************


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