How to calculate cumulative sum using Lag function?

[aman23]

How to calculate cumulative sum of below data using Lag function?

Name Marks

AA  50

BB 60

CC  70

DD 80

EE 90

FF 100

output should be:

Name Marks  Cumulative marks

AA    50   50

BB   60   110

CC   70  180

DD  80   260

EE  90  350

FF  100 450

[RW9]

Use retain, its what it is for:

data want;
  set have;
  retain cumulative_marks;
  cumulative_marks=ifn(_n_=1,marks,sum(sumulative_marks,marks));
run;

[aman23]

yes using retain can get the result, but can it be done using Lag function???

[RW9 · Accepted solution]

Like any problem, it can be done, but why on earth would you want to go through that?  You would need to create a lag statement specifically for each row of data as you cannot conditionally execute lag statements, so this would not work:

data want;
  set have;
  calc_marks=lag(calc_marks)+marks;
run;

If you try it you will get all kinds of weird results as the value used in the lag (which is a queue of values) does not work conditionally.

Use retain, its what its for.

[PaigeMiller]

data want;
  set have;
  cumulative_marks+marks;
run;

You don't need anything more complicated.

[novinosrin]

Hello @aman23  did this

  calc_marks=lag(calc_marks)+marks;

really work for your sample?