I am trying to get an output consisting of the number of elements needed to be added to sum a certain value.

Below is a sample code considered.

# value to reach
vTR = c(10,15,12,13,10,15,10)
# element to sum
element = c(9,6,5,2,1,9,1)
magicFoo(vTR, element)
# should return c(NA, 2, 3, 3, 4, 4, 2)
# 10 ~ NA, 15 <= 9+6, 12 <= 5+6+9, 13 <= 2+5+6, 10 <= 1+2+5+6...

For example, if I am looking for some kind of average where k is calculated dynamically I can do it with a for loop but I am finding a more elegant way to do this.

vTR = c(10,15,12,13,10,15,10)
# element to sum
element = c(9,6,5,2,1,9,1)
res = c()
j = 1
k = 0
sumE = 0
for (i in 1:length(vTR)){
k = k+1
sumE = sum(element[j:k])
if (sumE < vTR[i]) {
res[length(res)+1] = NA
next
}
repeat {
j = j + 1
sumE = sum(element[j:k])
if (sumE < vTR[i]) {
j = j-1
res[length(res)+1] = k-j +1
break
}
}
}
# > res
# [1] NA 2 3 3 4 4 2