Quick answer is your program was reading 3 lines at a time instead of the 2 lines that you data is using. So when it tried to read the last observation the data step stopped at the INPUT statement because it read past the end of the input file. So the last observation is never written to the output dataset.
Personally I would just read the file line by line. You can add a new variable to indicate which line is is for a particular id.
data want;
infile txt ;
input id $2. drug $1. sbp 8. dbp 8. ;
if id ne lag(id) then rep=1;
else rep+1;
run;
Results:
NOTE: 140 records were read from the infile TXT.
The minimum record length was 19.
The maximum record length was 19.
NOTE: The data set WORK.WANT has 140 observations and 5 variables.
First few observations:
Obs id drug sbp dbp rep
1 1 0 159.568 326.410 1
2 1 0 151.933 293.688 2
3 2 0 165.439 300.586 1
4 2 0 150.200 283.796 2
5 3 0 171.497 280.846 1
6 3 0 151.150 259.699 2
There is perhaps something wrong here as those pressure readings look wrong. You said that they values were 8 positions wide. But perhaps the values are something other than human blood pressure readings?
If you did want to read two lines at once you could just use the / cursor movement to go to the next line.
data want;
infile txt ;
input id $2. drug $1. sbp 8. dbp 8.
/ id2 $2. drug2 $1. spb2 8. dbp2 8.
;
if id ne id2 or drug ne drug2 then do;
put 'ERROR: There is a mismatch between the two lines. ' _n_= id= id2= drug= drug2= ;
delete;
end;
run;
Results:
NOTE: 140 records were read from the infile TXT.
The minimum record length was 19.
The maximum record length was 19.
NOTE: The data set WORK.WANT has 70 observations and 8 variables.
Values:
Obs id drug sbp dbp id2 drug2 spb2 dbp2
1 1 0 159.568 326.410 1 0 151.933 293.688
2 2 0 165.439 300.586 2 0 150.200 283.796
3 3 0 171.497 280.846 3 0 151.150 259.699
4 4 0 165.458 286.631 4 0 141.529 266.936
5 5 0 159.376 334.069 5 0 142.710 321.289
6 6 0 166.562 293.637 6 0 132.204 283.670
