CODEWITHSUNDEEP
r
sachinv
sachinv

Reputation: 502

Generate all combinations which sum to a value without repetitions in R

I have a vector and need to find all combinations where the sum is between a range.

set.seed(007)
w <- round(runif(10, 0, 1) * 100)
w
 [1] 99 40 12  7 24 79 34 97 17 46

I want a matrix of all combinations (without repetition) of these numbers in "w" whose sum is between 50 and 55 The matrix can contain values 0 and 1 whether the value at that position is to be considered in that solution

Eg: 0 1 1 0 0 0 0 0 0 0 means 40 and 12 are to be considered

There are many solutions available but they are using repetitions. I couldnt make out how to do this in R.

Any ideas.

Upvotes: 0

Views: 190

Answers (1)

Heroka
Heroka

Reputation: 13159

We can use combn, it creates combinations from a vector, without repetitions.

First, we create all combinations:

w_comb <- combn(w,2)

Then we test wether our combinations fullfill our constraints. We do this (thanks nicola) with colSums.

w_comb_tests <- colSums(w_comb) >= 50 & colSums(w_comb) <= 55

Finally, we generate a row of 0s and 1s for each selected combination:

res <- t(apply(w_comb[,w_comb_tests],2,function(x){
  as.numeric(w %in% x)
}))

Upvotes: 3

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