intck function not calculation intervals

[lady8506]

Here's my code below. Whenever I run it, the duration variable counts 0 for every observation in my dataset. Not sure why it's not calculating the duration in months between a patient's initial diagnosis date and the date of their death. Can someone take a look at my code and tell me if they see something wrong?

DATA survival_analysis; SET pancreas_temp4;

	duration = INTCK("DTMONTH", initial_dx_date1, coalesce(date_of_death1, date_last_fu_or_d1));
	put duration = ;

	IF vital_status1 = 0 or not missing(date_of_death1) then censored = 1;
	ELSE IF vital_status1 = 1 then censored = 0;

	LABEL duration = "Duration in Months";
RUN;

And here is a clip of the SAS log file: 

537 DATA survival_analysis; SET pancreas_temp4;
538
539 duration = INTCK("DTMONTH", initial_dx_date1, coalesce(date_of_death1,
539! date_last_fu_or_d1));
540 put duration = ;
541
542 IF vital_status1 = 0 or not missing(date_of_death1) then censored = 1;
543 ELSE IF vital_status1 = 1 then censored = 0;
544
545 LABEL duration = "Duration in Months";
546 RUN;

duration=0
duration=0
duration=0
duration=0
duration=0
duration=0
duration=0
duration=0
duration=0
duration=0
duration=0
duration=0

See all those lovely zeros? Why?! I checked all my dates and they are all the same format MMDDYY10, so I am not sure what's wrong. Any help is appreciated.

Also, here is some sample data.       1 = alive, 0 = dead          

vital_status1 initial_dx_date1 date_of_death1 date_last_fu_or_d1

1	08/02/2016	.	10/13/2017
0	02/25/2010	07/15/2010	07/15/2010
0	07/05/2010	.	08/14/2011
0	02/21/2012	07/11/2012	07/11/2012
0	03/24/2014	.	10/10/2014
1	02/03/2014	.	01/25/2018
1	01/30/2017	.	02/22/2018
0	06/15/2012	10/22/2013	10/22/2013
0	11/20/2009	06/10/2010	06/10/2010
0	10/21/2010	10/11/2015	10/11/2015
0	11/22/2011	07/28/2014	07/28/2014
1	05/22/2012	.	02/18/2014
0	07/08/2013	11/24/2013	11/24/2013
0	10/02/2013	12/25/2014	12/25/2014
0	05/17/2011	09/09/2016	09/09/2016
0	05/05/2011	09/10/2013	09/10/2013

[novinosrin · Accepted solution]

HI @lady8506  If your date values are SAS dates and not datetime why use DTMONTH

You should prolly use 'MONTH'

duration = INTCK("MONTH", initial_dx_date1, coalesce(date_of_death1,
539! date_last_fu_or_d1));

[lady8506]

Ha! Silly me! I knew it was something stupid that I was missing. Sometimes you can't see the forest through the trees! Thanks so much. This fixed the problem!

[novinosrin]

Lol I have had those moments too. Have a good day 🙂

[PaigeMiller]

Your data is SAS dates, not SAS date-time values. So you don't want to use DTMONTH in INTCK, you want to use MONTH

duration = INTCK("MONTH", initial_dx_date1, coalesce(date_of_death1, date_last_fu_or_d1));