could use proc sort nodupkey to reduce the mailing file to all the possible combinations of age/sex/ethnicity/occupation. And then merge this onto the master file.   proc sort data=mailingfile out=template (keep=age sex ethnicity occupation) nodupkey; by age sex ethnicity occupation; run;   proc sort masterfile by age sex ethnicity occupation;; run;   data new; merge masterfile template (in=a); by age sex ethnicity occupation; if a then output; run;   it deponds a lot on exactly what you're doing ie how they should be matched. You could do something sophisticated ie proc psmatch https://support.sas.com/documentation/onlinedoc/stat/142/psmatch.pdf ... View more

yes, just change to: if grp=1 then classc1=1; else classc1=0; if grp=2 then classc2=1; else classc2=0; ... View more

sorry, before the set statement put "retain cum_days". I'm surprised it worked at all without it(?) ... View more

i think there are many cro's (contract research organisations) in north carolina, very large and very small, they are maybe more likely to offer an intern than big pharma are. You could do some reading to prepare for the work environment eg companies have many standard operating procedures and SDTM, ADAM standards etc. A group like phuse can explain good programming practice (GPP): http://www.phusewiki.org/wiki/images/a/ae/Good_Programming_Practices_at_Every_Level.pdf https://www.lexjansen.com/phuse/2015/pp/PP25_ppt.pdf and they may have other resources on their website: https://www.phuse.eu/ if you want to get a sense of the regulatory requirements you can view fda reviews online: https://www.fda.gov/downloads/Drugs/DevelopmentApprovalProcess/DevelopmentResources/UCM251445.pdf although they are quite stats heavy ... View more