Lag function with multiple by group variables

[Saurabh_Rana]

I want the following output by using the lag function using multiple by variables.

A  B  C  Lag(C)

a  d  1       .

a  d  2       1

a  e  3       .

b  e  4       .

b  e  5       4

c  e  6       .

c  f   7       .

c  f   8       7

But the output I am getting is this-

A  B  C  Lag(C)

a  d  1       .

a  d  2       1

a  e  3       2

b  e  4       3

b  e  5       4

c  e  6       5

c  f   7       6

c  f   8       7

[andreas_lds]

Please post the code you have, so that we can suggest improvements.

Something like

if first.b then Lag_C = .;

should help.

[blueskyxyz]

data have;
    length a $1 b$1;
    input a b c;
cards;
a d 1
a d 2
a e 3
b e 4
b e 5
c e 6
c f 7
c f 8
;
proc sort; by  a b c; 
run;

data want;
    set have;
    by a b c;
    c_=lag(c);
run;

[andreas_lds]

---

@blueskyxyz wrote:

data have;
    length a $1 b$1;
    input a b c;
cards;
a d 1
a d 2
a e 3
b e 4
b e 5
c e 6
c f 7
c f 8
;
proc sort; by  a b c; 
run;

data want;
    set have;
    by a b c;
    c_=lag(c);
run;

---

This will not create the required dataset, but the one @Saurabh_Rana is getting now. Also: why is variable C in the the by-statement in proc sort? This seems to be wrong.

[Sajid01]

Hello @Saurabh_Rana 

The code is doing the way it is written.
You want the Lag(C) values for selected rows,

You need to define a criteria and add a filter for it in your code.

[Tom]

Why are those other values supposed to be missing?

Is it because you want to treat A and B as grouping variables?

data want;
  set have;
  by a b ;
  lag_c=lag(c);
  if first.b then lag_c=.;
run;

[ballardw]

---

@Saurabh_Rana wrote:

I want the following output by using the lag function using multiple by variables.

A  B  C  Lag(C)

a  d  1       .

a  d  2       1

a  e  3       .

b  e  4       .

b  e  5       4

c  e  6       .

c  f   7       .

c  f   8       7

But the output I am getting is this-

A  B  C  Lag(C)

a  d  1       .

a  d  2       1

a  e  3       2

b  e  4       3

b  e  5       4

c  e  6       5

c  f   7       6

c  f   8       7

---

So, what is the INPUT?

Which are the BY variables?

What are the assignment rules?