CODEWITHSUNDEEP
rsumsequencecumulative-sum
cornermountain
cornermountain

Reputation: 111

Cumulative sums in R

I want to compute the following term in R, but without using loops ("for" cycles):

enter image description here

So far, I already calculated it manually and tried to use sequence functions for both index variables i and j and integrated them in a cumsum function and summed up the returning vector.

i <- seq(1:10)
j <- seq(1:5)

sum(cumsum((i^5)/(10+j^i)))

However, the results do not match with my manual calculation, so this seems to be a wrong approach. Could anybody help me out on this?

Upvotes: 3

Views: 294

Answers (2)

ThomasIsCoding
ThomasIsCoding

Reputation: 101327

Try outer

> sum(outer(1:10, 1:5, FUN = function(i,j) i^5/(10+j^i)))
[1] 20845.76

Upvotes: 4

Edo
Edo

Reputation: 7818

Given

i <- seq(1:10)
j <- seq(1:5)

Solution 1:

ir <- rep(i, each = length(j))
jr <- rep(j, length(i))
sum(ir^5 / (10 + jr^ir))
#> [1] 20845.76

Solution 2:

d <- expand.grid(i=i,j=j)
with(d, sum(i^5 / (10 + j^i)))
#> [1] 20845.76

Solution 3: (@jogo)

sum(sapply(i, function(i) i^5 / (10+j^i)))
#> [1] 20845.76

Upvotes: 3

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