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mona4u
Lapis Lazuli | Level 10

 

Hi All, 

Below is an example of what I'm trying to achieve. My goal is to get the variable diff.  

 

X Y LAG DIFF
1 A    
2 A 1 1
3 A 2 1
4 A 3 1
5 A 4 1
1 B    
2 B 1 1
3 B 2 1
4 B 3 1
5 B 4 1

 

Mona 

3 REPLIES 3
Reeza
Super User

Why is the first diff 1 when there's no previous value?
If it's always 1 why is this needed? It would be good to include a use case that illustrates a different scenario.

 

I suspect this is what you're after?

data want;
set have;
by y;
_dif = dif(x);
_lag = lag(x);
if first.y then call missing(_dif, _lag);
run;

@mona4u wrote:

 

Hi All, 

Below is an example of what I'm trying to achieve. My goal is to get the variable diff.  

 

X Y LAG DIFF
1 A    
2 A 1 1
3 A 2 1
4 A 3 1
5 A 4 1
1 B    
2 B 1 1
3 B 2 1
4 B 3 1
5 B 4 1

 

Mona 


 

mona4u
Lapis Lazuli | Level 10

because I don't want to subtract different group values. 

 

the diff value not always 1 this is just dummy 

Reeza
Super User

Did you try the code posted?

I'm assuming groups are defined by Y as you never stated. I'm assuming you want the lag of the variable X, also not specifically stated. 

If the above is true the answer should be correct. Use the DIF/LAG function and reset at the first of each group. 

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