How to keep the previous value to the current one?

[Sikcion]

Hi guys! I am doing one sdtm project question,

there is one variable "folder" to keep the visiting week values like "week1" "screening" "week5";  also, we want to create a new variable "visitnum" to extract the numbers of folder, like if folder=week5, so we keep 5 for the visitnum;

when the folder="SRV", we want to keep the previous value of visitnum; like for observation80, we have folder="SRV", so we keep the previous obs(79) visitnum=43, and we get the visitnum=43+0.01;

I am trying to use RETAIN and lag function to keep the previous value, I don't know why the prev_visit value is correct, but the visitnum is keep the previous 2 value +0.01? like for the observation when prev_visit=43,  I hope to get visitnum=43.01 not 36.01.

Can you help me to fix it? Thank!

data vs_vs3;
set vs_vs2;
retain prev_visit;
length visit $14;
if first.vetest then prev_visit=.;

if folder="SCREENING" then do;
visitnum= -1;
visit="Screening";
end;

else if index(upcase(folder),"WEEK") then do;
visitnum= substr(folder,5)*7-6;
visit="Screening";
end;

else if index(upcase(folder),"SRV") then do;
visitnum = prev_visit +0.01;
visit="Systemic"||"-"||strip(put(visitnum,best12.));
end;

else if index(upcase(folder),"UNS")then do;
visitnum = prev_visit +0.01;
visit="Unsched"||"-"||strip(put(visitnum,best12.));
end;
prev_visit = lag(visitnum);
*drop prev_visit;
run;

[Kurt_Bremser]

I don't see the folder variable in your picture.

Do not post data in pictures. Post data as text, ideally in a DATA step with DATALINES. Use the "little running man" button to post code, it will keep the original formatting (which is eaten by the main posting window).

As long as we do not have usable data to work with (we can't copy/paste a picture into the program editor), it is hard to help you.