BookmarkSubscribeRSS Feed
ntburton1
Calcite | Level 5

I have data set that is set up as follows

ID Start_Date End_Date
1 25-Jan-17 25-Mar-17
1 1-Feb-17 14-Feb-17
2 1-Apr-17 30-Apr-17
2 15-Apr-17 20-Apr-17
2 1-Nov-17 25-Nov-17
3 16-Jun-17 20-Jun-17
4 1-May-17 20-May-17
4 21-May-17 30-May-17

 

 

I need to go from this, to one line of data for each ID that indicates/flags whether or not the ID had overlapping dates. For example: 

ID overlap_flag
1 1
2 1
3 0
4 0

 

I'm not sure how to do this in SAS, although I'm sure it's quite easy. Any suggestions? 

6 REPLIES 6
Kurt_Bremser
Super User

In a data step with by id:

- retain the flag variable

- retrieve the previous end_date with the lag() function.

- at first.id, set the flag to zero;

- if not first.id, compare the lagged end_date with the current start_date, and set flag to 1 if appropriate

- at last.id, output

- keep id and flag

ntburton1
Calcite | Level 5

hmmm I'm not sure I understand this. I'm a pretty novice SAS user and have never used the lag function. 

 

I'd have to sort on the start date first, no? Or does the lag function do this?

 

Many thanks for your assistance! 

Reeza
Super User

Yes you do need to sort, but your data was presented as sorted so in general we'll assume it's as shown. 

 

If you run into issues feel free to post your code and explain the issues. 

We're more than happy to assist, less happy to do your work 😉

 

 

error_prone
Barite | Level 11
Your data seems to be sorted by id and start_date - should be ok. Try to write the data step using the description provided by @Kurt_Bremser. Post code and log if you receive an error message.
Ksharp
Super User
data have;
infile cards expandtabs truncover;
input ID	Start_Date : date11.	End_Date : date11.;
format Start_Date End_Date : date11.;
cards;
1	25-Jan-17	25-Mar-17
1	1-Feb-17	14-Feb-17
2	1-Apr-17	30-Apr-17
2	15-Apr-17	20-Apr-17
2	1-Nov-17	25-Nov-17
3	16-Jun-17	20-Jun-17
4	1-May-17	20-May-17
4	21-May-17	30-May-17
;
run;
data temp;
 set have;
 by id;
 flag=(Start_Date<lag(End_Date));
 if first.id then flag=0;
run;
proc sql;
select id,max(flag) as flag
 from temp
  group by id;
quit;

sas-innovate-2024.png

Join us for SAS Innovate April 16-19 at the Aria in Las Vegas. Bring the team and save big with our group pricing for a limited time only.

Pre-conference courses and tutorials are filling up fast and are always a sellout. Register today to reserve your seat.

 

Register now!

How to Concatenate Values

Learn how use the CAT functions in SAS to join values from multiple variables into a single value.

Find more tutorials on the SAS Users YouTube channel.

Click image to register for webinarClick image to register for webinar

Classroom Training Available!

Select SAS Training centers are offering in-person courses. View upcoming courses for:

View all other training opportunities.

Discussion stats
  • 6 replies
  • 1233 views
  • 4 likes
  • 5 in conversation