topic Re: Prior and Post in SAS Procedures

Prior and Post

robertrao — Tue, 03 Dec 2013 16:09:07 GMT

Is my interpretation correct

if first date is 20th.could someone explain to me with example

/*date is WITHIN 5 days prior to the first_date*/

if date ge (first_date - 60*60*24*5)

/*date is WITHIN 5 days post to the first_date*/

if date le (first_date + 60*60*24*5) ;

Re: Prior and Post

art297 — Tue, 03 Dec 2013 16:18:07 GMT

If first_date is a datetime field, the comparisons are just adding or subtracting the number of seconds elapsed before or after a given date. However, neither is accounting for WITHIN a given time period as such a comparison would require three dates to be compared.

Re: Prior and Post

robertrao — Tue, 03 Dec 2013 16:26:30 GMT

first_date is a datetime field. and date is also date time field

i have two datetimess: date and first_date

i want to see if date is within +/- 5 days of first_date

and the below is for +5 or -5????

if date ge (first_date - 60*60*24*5)

Re: Prior and Post

Reeza — Tue, 03 Dec 2013 16:51:56 GMT

Is time a factor for these date time comparisons?

Re: Prior and Post

robertrao — Tue, 03 Dec 2013 16:57:15 GMT

Re: Prior and Post

art297 — Tue, 03 Dec 2013 18:29:16 GMT

Robert,

Be careful how you answer Fareeza'a question. It isn't a factor if your times are all zero but, if they do represent actual times, you could be misclassifying the differences. The following does consider time to be relevant:

data have;

informat date first_date datetime21.;

format date first_date datetime21.;

informat test_date date9.;

format test_date date9.;

input test_date span;

first_date=dhms(test_date,0,0,0);

date=dhms(test_date+span,0,0,0);

/*date is WITHIN 5 days prior to the first_date*/

prior=-5*60*60*24 le date-first_date le 0;

/*date is WITHIN 5 days post to the first_date*/

post=0 le date-first_date le 5*60*60*24;

cards;

03DEC2013 4

03DEC2013 6

03DEC2013 -4

03DEC2013 -6

;

If time really isn't relevant, and aren't all represented with zeros, than I'd suggest changing the formulas to compare the dateparts of the two fields and not adjusted for seconds.