Stata 15 help for sum()
[FN] Mathematical functions
Function
sum(x)
Description: the running sum of x, treating missing values as zero
For example, following the command generate y=sum(x),
the jth observation on y contains the sum of the first
through jth observations on x. See [D] egen for an
alternative sum function, total(), that produces a
constant equal to the overall sum.
Domain: all real numbers or missing
Range: 8e+307 to 8e+307 (excluding missing)
