if vtrack is defined with func="sum" , I would expect that if there are no values in the source of the vtrack in the given time.shift then the value 0 will be returned (and not NA).
Using this for example to count how many children a mother has previously had (need to support twins) - will never return 0
if vtrack is defined with func="sum" , I would expect that if there are no values in the source of the vtrack in the given time.shift then the value 0 will be returned (and not NA).
Using this for example to count how many children a mother has previously had (need to support twins) - will never return 0