derive start date and end date

[Jack2012]

HI All, 

I think this is q simple question, but uncertain how to work it out.  

So far as I recall, maybe use RETAIN, but have no clue on.  Hope someone can favor me. 

Thank you. 

Jack

/*-------------------------------------------------------*/

Below picture is the dummy data, I would like to record the same dose lifecycle trajactory. 

what I want to have is:

exdose  subjid  dose_st_dt   dose_en_dt

110mg  615010 2021-12-10  2022-01-19

0mg      615010 2022-01-20  2022-01-23 

110mg   615010 2022-01-24  2022-02-15

0mg      615010 2022-02-16   2022-02-22

55mg    615010 2022-02-23   2022-03-29

[PaigeMiller · Accepted solution]

From now on, please do not provide data as screen captures, we can't write programs to use screen capture data. Instead, we need data provided as SAS data step code which you can type in yourself, or via these instructions.

Also, it would help if you provided a clear description of how the final table is calculated from the input data. Don't make us guess, sometimes we get it wrong. 

So, without actual data, my code is UNTESTED. It is also based on my guesses as to what the method is, and maybe I guessed wrong.

data intermediate;
    set have;
    prev_exdose=lag(exdose);
    prev_subj=lag(subjid);
    if (exdose^=prev_exdose and subjid=prev_subj) or subjid^=prev_subj then group+1;
run;
proc summary data=intermediate nway;
    class group;
    id exdose subjid;
    var dose_st_dt dose_en_dt;
    output out=want min(dose_st_date)= max(dose_en_dt)=;
run;

[Jack2012]

OK. Thank you for your reminder.

VERY MUCH appreicated. That is what I want .

Thank you very much.

Jack.