Overlapping Dates- long to wide dataset

[ntburton1]

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? 

[Kurt_Bremser]

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]

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]

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 😉

[Kurt_Bremser]

My algorithm is complete. Translate it to SAS code, and post that here, so we can make the necessary corrections.

[error_prone]

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]

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;