SAS code to exclude observations that are out of order

[UcheOkoro]

Hello,

Please, I need help excluding observations from a variable that are out of order. For each ID, the order should be 010101 or 101010.  If the order is 001101, we exclude the repeated value, so it becomes 0101. The following is my sample data.

Thank you!

data WORK.CLASS(label='Student Data');
 input ID$3. Wgtloss;
 datalines;
222 0
222 1
222 1
222 0
222 0
222 0
223 1
223 1
223 1
223 0
223 0
223 1
224 1
224 1
224 0
224 1
224 0
224 0
 ;run;

[Tom · Accepted solution]

Seems like a simple application of BY group processing.  Use the NOTSORTED keyword on the BY statement to form the groups.

data have;
 input ID :$3. Wgtloss;
datalines;
222 0
222 1
222 1
222 0
222 0
222 0
223 1
223 1
223 1
223 0
223 0
223 1
224 1
224 1
224 0
224 1
224 0
224 0
;

data want;
  set have;
  by id wgtloss notsorted ;
  if first.wgtloss;
run;

Results

Obs    ID     Wgtloss

  1    222       0
  2    222       1
  3    222       0
  4    223       1
  5    223       0
  6    223       1
  7    224       1
  8    224       0
  9    224       1
 10    224       0

[UcheOkoro]

Thank you so much for your assistance!

[UcheOkoro]

Please, I have a follow up question. What if I want only the order where the number 1 comes first i.e. 101010?