CODEWITHSUNDEEP
rsimulation
Miao Cai
Miao Cai

Reputation: 1014

Randomly sample values from a pool so that the sum is less than a threshold in R

Let's say we have a pool of values and I want to sample random number of values from this pool, so that the sum of these values is between two thresholds. I want to design a function in R to implemented that.

pool = data.frame(ID = letters, value = sample(1:5, size = 26, replace = T))
> print(pool)
   ID  value
1  a     1
2  b     4
3  c     4
4  d     2
5  e     2
6  f     4
7  g     5
8  h     5
9  i     4
10 j     3
11 k     3
12 l     5
13 m     3
14 n     2
15 o     3
16 p     4
17 q     1
18 r     1
19 s     5
20 t     1
21 u     2
22 v     4
23 w     5
24 x     2
25 y     4
26 z     1

I want to randomly sample what ever number of IDs so that the sum of values for these IDs are between two thresholds, let's say between 8 and 10 (including the two boundaries). The expected outcome should be like these:

I think this question has not been asked previously. Does anyone have clues?

Upvotes: 0

Views: 630

Answers (1)

Jon Spring
Jon Spring

Reputation: 66415

Here's an approach where I shuffle the input and check the cumulative sum of the shuffled output to look for an acceptable sum.

If a subset of that initial sequence happens to work, it outputs that sequence (in this manifestation, the longest sequence under the max threshold). If it doesn't work, it reshuffles and looks again, up to the max number of iterations.

set.seed(42)
library(dplyr)
sample_in_range <- function(src_tbl, min_sum = 8, max_sum = 10, max_iter = 100) {
  for(i in 1:max_iter) {
    output <- src_tbl %>% 
      sample_n(nrow(src_tbl)) %>%
      mutate(ID = as.character(ID),
             cuml = cumsum(value)) %>%
      filter(cuml <= max_sum)
    if(max(output$cuml) >= min_sum) return(output)
  }
}

output <- sample_in_range(pool)
output
  ID value cuml
1  k     3    3
2  w     2    5
3  z     4    9
4  t     1   10

output %>% pull(ID)
[1] "k" "w" "z" "t"

Upvotes: 1

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