using fist.id for generating baseline value

[superbibi]

Hi Friends,

I have been trying to find the baseline value (say glucose) within one ID (hpbpid) using retain, by, etc. I am using SAS studio. The program just kept running without producing an output. I am wondering if there is endless loop in the code as below.

I have searched the sas communities, google, etc. I know there are many other ways to get the baseline value such as pro sql. I just want to know why my method does not work. 

Thank you.

Obs	hpbpid	date	glucose
1	19270818FM-B	16MAR2009	5
2	19270818FM-B	18JAN2011	5
3	19390310FMGL	07APR2008	5
4	19390310FMGL	24NOV2008	5
5	19390310FMGL	11MAR2009	6
6	19390325FCLB	01MAY2008	5
7	19390325FCLB	17MAR2009	5
8	19390507MJEM	14MAY2008	5
9	19390507MJEM	22SEP2008	0
10	19391013ME-D	11MAR2008	5

proc sort data = hpbp.lab_bio_demo;
by hpbpid date;
run;


data visit;
set hpbp.lab_bio_demo;
by hpbpid;
retain baseline_value;
if first.hpbpid then baseline_value  = glucose;
do until (last.hpbpid = 1);
baseline_value +0;
end;
run;

[novinosrin]

what is your expected/wanted output for the sample? plz

[Astounding]

Yes, your DO loop is endless.  Nothing inside the loop reads in any observations, so you can never get to the last.hpbpid observation.

The solution is simple.  Get rid of the DO loop and everything related to it.  The last statement in the DATA step should be:

if first.hpbpid then baseline_value  = glucose;

(Don't remove the RUN statement, however.)

[superbibi]

Hi Astounding, 

The code works great! Thank you so so much!

May I ask one more question regarding the do loop? If I want to generate a count column from 1 to the number of the last.id using the do loop, how should I modify the do loop code? For example, in the example dateset, there are two duplicates in the first ID, then the count should be 1 and 2. Thank you.

[Astounding · Accepted solution]

One way to handle that:

if first.hpbpid then do;
   baseline_value = glucose;
   count = 1;
end;
else count + 1;

[superbibi]

Excellent! Thank you very much!