topic Re: Randomly Select an Element of an Array in SAS Programming

Randomly Select an Element of an Array

lhsumdalum — Fri, 23 Feb 2018 20:36:08 GMT

Hi,

I have an array of length n, for example :

ARRAY _Example{*} 6$ EXA001:

I want to randomly select an element of the array. Is there an easy or straight forward way of achieving this?

The larger scope of this issue is that I want to assign a random element of the the array (map the element for example EXA004) to a dataset. Essentially, randomly assign one of the elements of the array to an ID variable.

Any insight into this issue would be much appreciated.

Cheers.

Re: Randomly Select an Element of an Array

Astounding — Fri, 23 Feb 2018 20:50:20 GMT

Assuming that the syntax for the array statement gets fixed ...

data want;

set have;

array _Example {*} whatever goes here;

r = ceil( dim(_Example) * ranuni(12345) ) ;

randomly_selected_element = _Example{r};

run;

The variable R will be a randomly selected integer, minimum is 1 and maximum is number of elements in the array.

Re: Randomly Select an Element of an Array

Reeza — Fri, 23 Feb 2018 20:51:02 GMT

1. Generate a random uniform variable between 1 and 6. This assumes you're using SAS 9.4 TS1M4+, if you don't, use the approach outlined here

rand_int = rand('Integer', 1, 6);

2. Use that index in the array to map the value over.

value = _example(rand_int);

@lhsumdalum wrote:

Hi,

I have an array of length n, for example :
ARRAY _Example{*} 6$ EXA001: 
I want to randomly select an element of the array. Is there an easy or straight forward way of achieving this?

The larger scope of this issue is that I want to assign a random element of the the array (map the element for example EXA004) to a dataset. Essentially, randomly assign one of the elements of the array to an ID variable.

Any insight into this issue would be much appreciated.

Cheers.

Re: Randomly Select an Element of an Array

lhsumdalum — Fri, 23 Feb 2018 20:56:03 GMT

Is it possible to replace the hard-coded upper bound of 6 with the unspecified dimension of the array? To continue your example, as such:

rand_int = rand('Integer', 1, dim(_Example));

Re: Randomly Select an Element of an Array

Reeza — Fri, 23 Feb 2018 21:00:51 GMT

I don't know, did it work?

@lhsumdalum wrote:

Is it possible to replace the hard-coded upper bound of 6 with the unspecified dimension of the array? To continue your example, as such:
rand_int = rand('Integer', 1, dim(_Example));

Re: Randomly Select an Element of an Array

lhsumdalum — Fri, 23 Feb 2018 21:27:19 GMT

The test that I tried with this logic will not populate the random_element column with the array element.

data test; 
	array _Example{*} $6. TEST01-TEST10 ; 
	r = ceil(dim(_Vendor) * ranuni(12345)); 
	random_element = _Example{r}; 
run;

I appreciate your help, please bear with me as I am a new SAS user.

Re: Randomly Select an Element of an Array

Reeza — Fri, 23 Feb 2018 21:42:49 GMT

You don't have a SET statement. Don't you have an input dataset?

Re: Randomly Select an Element of an Array

lhsumdalum — Fri, 23 Feb 2018 21:46:33 GMT

I do have an input dataset that I want to map the elements of the value column in the above example to. However, I needed to create the array myself. I was planning on using a proc sql to join the elements of the value column to the existing data set.

Re: Randomly Select an Element of an Array

Reeza — Fri, 23 Feb 2018 21:54:24 GMT

You lost me now.

I still suspect you need to add the SET statement.

OR if you're creating a new data set from scratch you need a loop with an output statement.

do i=1 to 1000; *number of records;
x= .... ;
output;
end;