I want to randomly select a single value of a variable in Stata in order to e.g. delete it in a simulation/bootstrap.

Stata offers simple ways of creating subsamples from a dataset using:

With replacement use:

bsample

Without replacement:

sample

However, it seems a bit more involved to get a random selection from a list of numbersÂ *not in the dataset*.

This is what I tried to pick a number from a list of numbers at random – undoubtedly to cumbersome.

1) Create a list of random numbers, which is has as many entries as the list you want to select from

foreach num of local listtoselectfrom {
local randomnumber = runiform()
local rnumbers = "`rnumbers'`randomnumber' "
}

2) Sort the list of random numbers

local selection : list sort renumbers

3) Select the lowest random number

local posofselected = word("`selection'",1)

4) Find the position of this lowest random number in the *unsorted* list of random numbers

local posinselectionlocal : list posof "`posofselected'" in rnumbers

5) Use this position to select at random ONE item from the list you want to select from:

local randomitem : word `posinselectionlocal' of `listtoselectfrom'

Example

set seed 7492001 //For replicability.
local listtoselectfrom = " 1 3 4 5 9 10"
foreach num of local listtoselectfrom {
local randomnumber = runiform()
local rnumbers = "`rnumbers'`randomnumber' "
}
local selection : list sort rnumbers
local posofselected = word("`selection'",wordcount("`selection'"))
local posinselectionlocal : list posof "`posofselected'" in rnumbers
local randomitem : word `posinselectionlocal' of `listtoselectfrom'
dis "This is the selected number: `randomitem'"

**P.S. More than one number**

The select more than one number, select more numbers from the random number list in 3). And change loop over their positions using step 4) and 5).

**Reference:**

The described procedure was inspired by following two posts:

1) http://whatthestats.wordpress.com/2012/08/07/stata-selecting-random-samples/

2) http://blog.stata.com/2012/07/18/using-statas-random-number-generators-part-1/

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