topic Re: generate sequence in SAS Procedures

generate sequence

molla — Mon, 21 Nov 2016 12:21:43 GMT

Hi,

I have the following dataset

student_id

I need the output as

student_id seq_num

1 1

2 2

3 3

4 4

1 1

2 2

3 3

1 1

2 2

3 3

1 1

2 2

Re: generate sequence

Kurt_Bremser — Mon, 21 Nov 2016 12:29:17 GMT

Ahem,

seq_num = student_id;

Re: generate sequence

RW9 — Mon, 21 Nov 2016 12:43:32 GMT

Not sure what your question here is. You have one variable and need to create another variable which is exactly the same as the variable you have? Maybe your required output is not correct, and you need the sequence within each by group? If so:

data want;
  set have;
  do seq_num=1 to 4;
    output;
  end;
run;

Re: generate sequence

mkeintz — Mon, 21 Nov 2016 13:01:21 GMT

I think what you really want is to track the order in which id's first appear, yes? I.e.if you have

AAA

A21

BBB

CCC

A21

BBB

AAA

...

then do you wnat id=AAA seq=1, id=A21 seq=2, id=BBB seq=3, id=CCC seq=4.

If so then this would work:

data want (drop=rc);
  set have;
  if _n_=1 then do;
    declare hash id_lookup();
      id_lookup.definekey('id');
      id_lookup.definedata('seq');
      id_lookup.definedone();
  end;
  rc=id_lookup.find();
  if rc^=0 then do;
    seq=id_lookup.num_items+1;
    rc=id_lookup.add();
  end;
run;

Re: generate sequence

Astounding — Mon, 21 Nov 2016 15:33:33 GMT

Here's an idea:

data want;

set have;

seq_num + 1;

if student_id < lag(student_id) then seq_num=1;

run;

It's not 100% clear when to start the SEQ_NUM values over again, but this might be sufficient.

Re: generate sequence

mkeintz — Mon, 21 Nov 2016 15:49:14 GMT

I think the OP wants to set up a lookup table, in which each ID is assigned a unique sequence number, with this additional propert: the sequence number will rank the order of first appearance of the ID.