topic Re: Count number of times variables changes from 0 to 1 in SAS Programming

Count number of times variables changes from 0 to 1

malena — Mon, 06 Jun 2016 20:12:30 GMT

I have a dataset of 25000 records with this layout;

ID DOC25 DOC26 DOC27 DOC28 DOC29 ........ DOC48

1 0 1 1 0 1 0

DOC25-DOC48 are montly counts which have 0 if the person was on the streets, 1 if incarcerated

DOC25 corresponds to January 2013

DOC48 corresponds to December 2014

I want to count how many times was a person incarcerated but if the person remains in prison longer than 1 month, the following months will be 1 as well until it changes to 0 when release, here in December 2014. So I want to keep track only of the first time the value changes

thanks!

Re: Count number of times variables changes from 0 to 1

Reeza — Mon, 06 Jun 2016 20:24:34 GMT

The logic is if the variable value doesn't equal the previous value. You've had previous answers that demonstrate a loop over the values

and declaring an array so this should be enough to get started.

If doc(i) ne doc(i-1) then flag_count+1;

Re: Count number of times variables changes from 0 to 1

Astounding — Mon, 06 Jun 2016 21:00:04 GMT

Sounds like this should do it within a DATA step:

array docs {*} doc25-doc48;

incarcerated=0;

do i=2 to 24;

if docs{i}=1 and docs{i-1}=0 then incarcerated + 1;

end;

This assumes that if DOC25=1 then you don't want to count it as an incarceration. If that's wrong, it's easy enough to change.

Re: Count number of times variables changes from 0 to 1

PGStats — Mon, 06 Jun 2016 21:29:01 GMT

@Astounding wrote:

This assumes that if DOC25=1 then you don't want to count it as an incarceration. If that's wrong, it's easy enough to change.

The alternative would require changing

incarcerated=0;

incarcerated=docs{1};

Re: Count number of times variables changes from 0 to 1

RW9 — Tue, 07 Jun 2016 08:53:32 GMT

As an alternative:

data want;
  doc1=0; doc2=1; doc3=1; doc4=0; doc5=1;
  test=count(cats(of doc:),"01");
run;

Re: Count number of times variables changes from 0 to 1

PGStats — Tue, 07 Jun 2016 14:44:26 GMT

Or again, if you want to count initial incarcerations

data want;
  doc1=0; doc2=1; doc3=1; doc4=0; doc5=1;
  test=count(cats("0", of doc:),"01");
run;