02-04-2015 08:17 AM
I have a little issue and I can't clear in how to resolve it.
lets say that I have the following data set :
input subject $1-3 dtc $4-24 ;
I would like to calculate the minimum date for this subject. In order to do so I have to convert date into a datetime type in order to compare them.
data test_v; set visit ;
/*create a new dtc_up that will complete dtc*/
if count(dtc,':') eq 2 then dtc_up=dtc;
if count(dtc,':') eq 1 then dtc_up=compress(dtc!!":00");
else if count(dtc,':') eq 0 then do ;
if count(dtc,'-') eq 2 then dtc_up=compress(dtc!!"T00:00:00");
else if count(dtc,'-') eq 1 then dtc_up=compress(dtc!!"-01T00:00:00");
else if count(dtc,'-') eq 0 and not missing(dtc) then dtc_up=compress(dtc!!"01-01T00:00:00");
else call missing(dtc_up);
if not missing(dtc_up) then dt_anydtm=input(dtc_up,anydtdtm.);
else call missing(dt_anydtm);
Once I have done this I use a proc sql statement to compute the minimum:
create table min as
select subject, min(dt_anydtm) as svstdtc format=IS8601DT.
group by subject;
Problem, from which record is the minimum value taken from ???? From record 1, from record 2 or from record 3 ? I need to know that because I'll create a new char variable called SVSTDTC which will capture the original minimum value.
For those who are familiar to CIDSC I am trying to bild an SV domain.
By the way can SAS compare 2014-01-15 with 2014-01-15T00:00 without performing the datastep above and decide which is the minimum value ?
Thanks in advance,
02-04-2015 08:29 AM
Well, firstly your code can be shrunk down into the one proc sql:
create table WANT as
select MIN(DTC) as MIN_DTC format=datetime.,
MAX(DTC) as MAX_DTC format=datetime.
from (select case when length(strip(DTC))=10 then input(strip(DTC)||"T00:00:00",e8601dt.)
when length(strip(DTC))=16 then input(strip(DTC)||":00",e8601dt.)
else input(DTC,e8601dt.) end as DTC from VISIT);
As for what to do about comparisons, this is really up to what your company/project team decide. There are several options:
Only compare where full date and time present.
Only compare dates.
Compare date/times and populate time with a fixed timepoint if missing.
We can't really tell you which one to choose as that would be on a per-study basis.
As for CDISC - SDTM, sorting and such like is done on the text value as it is. For Adam, then it should be per the rules in you stats plan.