make a variable based on a cumulative sum with reset based on condition

Question

I want a variable such as desired_output, based on a cumulative sum over cumsumover, where the cumsum function resets every time it reaches the next number in thresh.

cumsumover <- c(1, 2, 7, 4, 2, 5)
thresh <- c(3, 7, 11)
desired_output <- c(3, 3 ,7 ,11 ,11 ,11) # same length as cumsumover

This question is similar, but I can't wrap my head around the code. dplyr / R cumulative sum with reset

Compared to similar questions my condition is specified in a vector of different length than the cumsumover.

Any help would be greatly appreciated. Bonus if both a base R and a tidyverse approach is provided.

Ronak Shah · Accepted Answer · 2018-10-20T06:52:32.320

2

In base R, we can use cut with breaks as thresh and labels as letters of same length as thresh.

cut(cumsum(cumsumover),breaks = c(0, thresh[-1], max(cumsum(cumsumover))),
          labels = letters[seq_along(thresh)])

#[1] a a b c c c

Replaced the last element of thresh with max(cumsum(cumsumover)) so that anything outside last element of thresh is assigned the last label.

If we want labels as thresh instead of letters

cut(cumsum(cumsumover),breaks = c(0, thresh[-1], max(cumsum(cumsumover))),labels = thresh)
#[1] 3  3  7  11 11 11

edited Oct 20 '18 at 06:52

answered Oct 19 '18 at 11:02

Ronak Shah

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I added a more general example, because I got the error: `'breaks' are not unique` – dzgreen Oct 20 '18 at 13:27
@dzgreen it is not advisable to continuously change your question. Each question should be solving only one unique problem. I would suggest you to ask a new question. – Ronak Shah Oct 20 '18 at 13:43
I will do that. Thanks for the advise. – dzgreen Oct 20 '18 at 13:52

score 0 · Answer 2 · answered Oct 19 '18 at 11:48

Here is another solution:

data:

cumsumover <- c(1, 2, 7, 4, 2, 5)
thresh     <- c(3, 7, 11)

code:

outp <- letters[1:3] # to make solution more general
cumsumover_copy <- cumsumover  # I use <<- inside sapply so therefore I make a copy to stay save

unlist(
sapply(seq_along(thresh), function(x) {
    cs_over <- cumsum(cumsumover_copy)
    ntimes = sum( cs_over <= thresh[x] )
    cumsumover_copy <<- cumsumover_copy[-(1:ntimes)]
    return( rep(outp[x], ntimes) )
                             } )
)

result:

#[1] "a" "a" "b" "c" "c" "c"

score 0 · Answer 3 · answered Oct 20 '18 at 12:24

Using .bincode you can do this:

thresh[.bincode(cumsum(cumsumover), c(-Inf,thresh[-1],Inf))]
[1]  3  3  7 11 11 11

.bincode is used by cut, which basically adds labels and checks, so it's more efficient:

 x <-rep(cumsum(cumsumover),10000)
microbenchmark::microbenchmark(
  bincode   = thresh[.bincode(x, c(-Inf,thresh[-1],Inf))],
  cut       = cut(x,breaks = c(-Inf, thresh[-1], Inf),labels = thresh))
# Unit: microseconds
#     expr    min      lq     mean  median      uq     max neval
#  bincode  450.2  459.75  654.794  482.10  642.20  5028.4   100
#      cut 1739.3 1864.90 2622.593 2215.15 2713.25 12194.8   100

make a variable based on a cumulative sum with reset based on condition

3 Answers3