Identifying onset in longitudinal data

[lalaktgrau]

Hi all,

I have longitudinal data (one obs per person per minute) with the variables: ID, DateTime, and Disease. Disease is binary.

How can I identify the first occurrence of disease in this longitudinal data?

Thanks

[novinosrin]

Plz post samples of your input and your required output?

Sure some genuises may be gauge from sentence based description but samples help test the solutions from responder's end 

[lalaktgrau]

data WORK.CLASS;
infile datalines truncover;
input Name:$8. disease datetime;
informat datetime datetime20.;
format datetime datetime20.;
datalines;
Alfred 0 04MAR14:23:55:00
Alfred 0 04MAR14:23:56:00
Alfred 1 04MAR14:23:57:00
Alfred 1 04MAR14:23:58:00
Alfred 1 04MAR14:23:59:00
Alfred 1 04MAR14:00:00:00
Alfred 1 04MAR14:01:01:00
Alfred 1 04MAR14:01:02:00
Alfred 1 04MAR14:01:03:00
Alfred 1 04MAR14:01:04:00

mary 0 04MAR14:23:55:00
mary 0 04MAR14:23:56:00
mary 0 04MAR14:23:57:00
mary 0 04MAR14:23:58:00
mary 0 04MAR14:23:59:00
mary 1 04MAR14:00:00:00
mary 1 04MAR14:01:01:00
mary 1 04MAR14:01:02:00
mary 1 04MAR14:01:03:00
mary 1 04MAR14:01:04:00
;

I'd like a variable that =1 just on the FIRST time disease=1. For example, the variable would =1 for Alfred at '04MAR14:23:57:00' and =1 for Mary at ' 04MAR14:00:00:00'

[novinosrin]

 
data WORK.CLASS;
infile datalines truncover;
input Name:$8. disease datetime;
informat datetime datetime20.;
format datetime datetime20.;
datalines;
Alfred 0 04MAR14:23:55:00
Alfred 0 04MAR14:23:56:00
Alfred 1 04MAR14:23:57:00
Alfred 1 04MAR14:23:58:00
Alfred 1 04MAR14:23:59:00
Alfred 1 04MAR14:00:00:00
Alfred 1 04MAR14:01:01:00
Alfred 1 04MAR14:01:02:00
Alfred 1 04MAR14:01:03:00
Alfred 1 04MAR14:01:04:00
mary 0 04MAR14:23:55:00
mary 0 04MAR14:23:56:00
mary 0 04MAR14:23:57:00
mary 0 04MAR14:23:58:00
mary 0 04MAR14:23:59:00
mary 1 04MAR14:00:00:00
mary 1 04MAR14:01:01:00
mary 1 04MAR14:01:02:00
mary 1 04MAR14:01:03:00
mary 1 04MAR14:01:04:00
;

data want;
set class;
by name;
if first.name then temp=1;
temp+disease;
if temp=2;
drop temp;
run;

[lalaktgrau]

This works... but what if a person can fall in and out of disease? How can I identify each individual onset?

[novinosrin]

Can you clarify that point and post your required output plz

[lalaktgrau]

data WORK.CLASS;
infile datalines truncover;
input Name:$8. disease datetime;
informat datetime datetime20.;
format datetime datetime20.;
datalines;
Alfred 0 04MAR14:23:55:00
Alfred 0 04MAR14:23:56:00
Alfred 1 04MAR14:23:57:00
Alfred 1 04MAR14:23:58:00
Alfred 0 04MAR14:23:59:00
Alfred 0 04MAR14:00:00:00
Alfred 1 04MAR14:01:01:00
Alfred 1 04MAR14:01:02:00
Alfred 1 04MAR14:01:03:00
Alfred 1 04MAR14:01:04:00

mary 0 04MAR14:23:55:00
mary 0 04MAR14:23:56:00
mary 0 04MAR14:23:57:00
mary 0 04MAR14:23:58:00
mary 0 04MAR14:23:59:00
mary 1 04MAR14:00:00:00
mary 0 04MAR14:01:01:00
mary 0 04MAR14:01:02:00
mary 1 04MAR14:01:03:00
mary 1 04MAR14:01:04:00
;

If we wanted the variable to =1 each time there is a new onset of disease? Changing from 0 to 1?

[novinosrin]

Do you mean you want to pick all the 1's? 

An output sample for the input would help

[lalaktgrau]

I would want a variable to equal 1 whenever there is a change from 0 to 1.

[novinosrin]

may be this?

data WORK.CLASS;
infile datalines truncover;
input Name:$8. disease datetime;
informat datetime datetime20.;
format datetime datetime20.;
datalines;
Alfred 0 04MAR14:23:55:00
Alfred 0 04MAR14:23:56:00
Alfred 1 04MAR14:23:57:00
Alfred 1 04MAR14:23:58:00
Alfred 0 04MAR14:23:59:00
Alfred 0 04MAR14:00:00:00
Alfred 1 04MAR14:01:01:00
Alfred 1 04MAR14:01:02:00
Alfred 1 04MAR14:01:03:00
Alfred 1 04MAR14:01:04:00
mary 0 04MAR14:23:55:00
mary 0 04MAR14:23:56:00
mary 0 04MAR14:23:57:00
mary 0 04MAR14:23:58:00
mary 0 04MAR14:23:59:00
mary 1 04MAR14:00:00:00
mary 0 04MAR14:01:01:00
mary 0 04MAR14:01:02:00
mary 1 04MAR14:01:03:00
mary 1 04MAR14:01:04:00
;

data want;
set class;
by name disease notsorted;
if first.disease and disease then flag=1;
run;

[mkeintz · Accepted solution]

data WORK.CLASS;
infile datalines truncover;
input Name:$8. disease datetime;
informat datetime datetime20.;
format datetime datetime20.;
datalines;
Alfred 0 04MAR14:23:55:00
Alfred 0 04MAR14:23:56:00
Alfred 1 04MAR14:23:57:00
Alfred 1 04MAR14:23:58:00
Alfred 0 04MAR14:23:59:00
Alfred 0 04MAR14:00:00:00
Alfred 1 04MAR14:01:01:00
Alfred 1 04MAR14:01:02:00
Alfred 1 04MAR14:01:03:00
Alfred 1 04MAR14:01:04:00
mary 0 04MAR14:23:55:00
mary 0 04MAR14:23:56:00
mary 0 04MAR14:23:57:00
mary 0 04MAR14:23:58:00
mary 0 04MAR14:23:59:00
mary 1 04MAR14:00:00:00
mary 0 04MAR14:01:01:00
mary 0 04MAR14:01:02:00
mary 1 04MAR14:01:03:00
mary 1 04MAR14:01:04:00
;

data want;
  set class;
  by name;
  flag= (first.name=1 and disease=1) or (dif(disease)=1);
run;

The DIF function is defined as   dif(x)=x-lag(x).  So the condition "dif(disease)=1" picks up all instances of disease=1 that immediately follow a disease=0.