topic Data step in SAS Programming

Data step

spdattani — Sun, 04 Mar 2018 10:26:04 GMT

Hi every one I wanted to know how do i find the new data entry of the week ?

For Example My data looks like this

Input :

Week Patient

W1 P1

W1 P2

W1 P3

W2 P1

W2 P2

W2 P4

W3 P3

W3 P4

W3 P5

Desired output

Week Patient Flag

W1 P1

W1 P2

W1 P3

W2 P1

W2 P2

W2 P4 New

W3 P3

W3 P4

W3 P5 New

Basically if i am finding the new patient in w6 then I have to look back all possible week and compare how many of these patients have visited me before W6 and if there a new which was not there till w6 then I have to mark that one as a new patient

The weekly data set I have is huge I there is no way i can write individual subset code for everyone

any help will be much appreciated

Thanks in advance

Re: Data step

Astounding — Sun, 04 Mar 2018 13:23:03 GMT

It looks like you have a second, unwritten rule here: Don't mark anybody in W1 as "New".

To get the result you are asking for:

proc sort data=have;

by patient week;

run;

data want;

set have;

by patient week;

if first.patient and week ne 'W1' then flag='New';

run;

There is a hidden pitfall here. This program assumes that the weeks go as high as 9, but no higher. Otherwise the sorted order would be wrong:

W10

W11

If you have more than 9 weeks, you would need to extract a numeric variable from WEEK:

weeknum = input( substr(week,2), 2.);

Then use WEEKNUM instead of WEEK for sorting.

Re: Data step

novinosrin — Sun, 04 Mar 2018 19:32:50 GMT

data have;
input (Week   Patient) ($) ;
datalines;
W1          P1
W1          P2
W1          P3 
W2          P1   
W2          P2 
W2          P4
W3          P3
W3          P4
W3          P5
;
data want;
if _n_=1 then do;
if 0 then set have;
 dcl hash h();
 h.definekey('patient');
 h.definedone();
 end;
 set have end=last;
 by Week   Patient;
 length Flag $10;
 call missing(Flag);
 if first.week then _n+1;
if _n>1 then do; 
if h.check() ne 0 then Flag='NEW';
end;
h.replace();
drop _:;
run;

Re: Data step

SuryaKiran — Sun, 04 Mar 2018 19:39:16 GMT

Check this out.

Data have;
infile datalines dlm=" ";
input Week $ Patient $;
datalines; 
W1 P1
W1 P2
W1 P3
W2 P1
W2 P2
W2 P4
W3 P3
W3 P4
W3 P5
;
run;

PROC SORT DATA=HAVE;
BY WEEK;
RUN;
%LET Patient_List=PATIENTS;
DATA WANT;
SET HAVE ;
IF FIND(SYMGET("Patient_List"),STRIP(PATIENT))=0 
		THEN DO;
			CALL SYMPUT("Patient_List",CATX(',',SYMGET("Patient_List"),PATIENT));
			FLAG="NEW";
		END;
IF WEEK="W1" THEN FLAG="";
RUN;

Re: Data step

novinosrin — Sun, 04 Mar 2018 19:52:43 GMT

arrays:

data have;
input (Week   Patient) ($) ;
datalines;
W1          P1
W1          P2
W1          P3 
W2          P1   
W2          P2 
W2          P4
W3          P3
W3          P4
W3          P5
;

data want;
do _n_=1 by 1 until(eof);
set have end=eof;
by Week   Patient;
array temp(1000)$ _temporary_ ;/*arbitrary subscript value*/
length Flag $10;
call missing(Flag);
if first.week then _n+1;
if _n=1 then temp(_n_)=Patient;
else if _n>1 and patient not in temp then do; Flag="NEW";temp(_n_)=Patient;end;
output;
end;
drop _:;
run;

Re: Data step

Astounding — Mon, 05 Mar 2018 14:20:13 GMT

A quick follow-up here ... SAS provides a way that you can sort character values but make "W9" sort before "W10". Here's the revised solution:

proc sort data=have sortseq=linguistic (numeric_collation=on);

by patient week;

run;

data want;

set have;

by patient;

if first.patient and week ne 'W1' then flag='New';

run;

Note that the second BY statement has changed as well.