Who do I "concatenate" missing visit data?

[nyitray]

I’m doing analysis on a longitudinal study with up to 10 visits for some participants. Some data are missing.  If data for a participant are not missing at a subsequent visit, then that subsequent visit data needs to replace the prior missing data.  For example, participant A might have missed visit 1 but attended visits 2 through 10. I need the nonmissing data in vists 2-10 to concatenate left (or ‘shift’ to the left) so there are nonmissing data in vists 1-9 and one missing datum in visit 10. Of course, missing data could occur at any visit. All variable names have a suffix identifying visit number. Below is an example using numeric data (for example, positive or negative blood tests at each of ten visits); however, variables could be character or numeric. All help on this is appreciated - I wonder now if converting this wide data to long form is the first step...

Data Have

Obs x_v1 x_v2 x_v3 x_v4 x_v5 x_v6 x_v7 x_v8 x_v9 x_v10

1      .    1    0    1    0    1    0    1    0     1

2      0    .    1    0    0    .    .    1    0     0

3      .    1    0    1    0    1    0    1    0     .

Data Want

Obs x_v1 x_v2 x_v3 x_v4 x_v5 x_v6 x_v7 x_v8 x_v9 x_v10

1      1    0    1    0    1    0    1    0     1    .

2      0    1    0    0    1    0    0    .     .    .

3      1    0    1    0    1    0    1    0     .    .

[Linlin · Accepted solution]

data have;

input id x_v1 x_v2 x_v3 x_v4 x_v5 x_v6 x_v7 x_v8 x_v9 x_v10;

cards;

1 .    1    0    1    0    1    0    1    0     1

2 0    .    1    0    0    .    .    1    0     0

3 .    1    0    1    0    1    0    1    0     .

;

data long(keep=id v);

  set have;

  array x(*) x_v1-x_v10;

  do _n_=1 to dim(x);

  v=x(_n_);

  if not missing(v) then output;

  end;

  run;

data want(drop=v count);

retain x_v1-x_v10;

array x x_v1-x_v10;

  set long;

  by id notsorted;

  if first.id then count=0;

  count+1;

  x(count)=v;

  if last.id then do;

      output;

   call missing (of x(*));

   end;

  run;

proc print;run;

Linlin

[nyitray]

Thanks Linlin!  This worked quite well.  Alan

[Haikuo]

Or you can try this:

data have;

input id x_v1 x_v2 x_v3 x_v4 x_v5 x_v6 x_v7 x_v8 x_v9 x_v10;

cards;

1 .    1    0    1    0    1    0    1    0     1

2 0    .    1    0    0    .    .    1    0     0

3 .    1    0    1    0    1    0    1    0     .

;

data want (drop=_:);

set have;

length _t $50.;

  array old x_v1-x_v10;

  _t=catx(' ',of old(*));

  _n=n(of old(*));

  call missing(of old(*));

do _n_=1 to _n;

  old(_n_)=scan(_t,_n_);

end;

run;

proc print;run;

Haikuo