How to set subsequent values to missing and keep first occurence

[SimRock]

Hi I am trying to keep the first occurence of a variable and set the subsequent values of the variables to missing

My data looks like this

Data have;

input  id time AMI;

datalines;

 1 1  0

 1 2  0

 1 3  1

 1 4  0

 2  1  1

 2  2  0

 2  2  1

 2  4  0

run;

I would like my data to look like this

ID time AMI

 1 1  0

 1 2  0

 1 3  1

 1 4  .

 2  1  1

 2  2  .

 2  2  .

 2  4  .

Basically, I only want to assess the first occurence of AMI

Thank you

[Shmuel · Accepted solution]

Assuming data is sorted by ID you can do:

data want;

 set have;

  by ID;

       retain flag; drop flag;

      if first.id then flag=0;

      if flag=1 then ami=.;

      if ami=1 and flag=0 then flag=1;

run;

[SimRock]

Thank you very Shmuel. It works perfectly

Best

[PGStats]

I would do:

data want;
do until(last.id);
    set have; by id;
    if AMImet 
        then call missing(newAMI);
        else newAMI = AMI;
    output;
    if AMI then AMImet = 1;
    end;
drop AMI AMImet; rename newAMI=AMI;
run;

[SimRock]

Thank you very PGStats. Your codes works awesome too.

Thanks so much

Best