CODEWITHSUNDEEP
r
davo1979
davo1979

Reputation: 231

Calculate cumulative percentage for all elements of vector

I'm not sure why I can't wrap my head around this, but maybe someone can help. I've done the following using a for loop:

v <- c(500,498,457,400,376,300,210,157,64,10,2,2,2,1,1,1,1,1,1,1)
partsum <- 0
total <- sum(v)
percov <- numeric()
for (i in 1:length(v)){
        partsum <- partsum + v[i]
        percov[i] <- 100 * partsum/total
}
percov

However, I am dealing with a massive amount of data, and the for loop is quite slow. I feel like there definitely has to be another way to do this in R, and it might be faster. Something like:

percov <- 100 * partsum/sum(v)

where partsum at each element's index is the sum of all elements of v that are greater than or equal to the value of v for that element. But how would I do that?

Upvotes: 4

Views: 4596

Answers (1)

akrun
akrun

Reputation: 887991

We can divide the cumulative sum (cumsum) of the vector by the sum of the vector and multiply by 100

percovN <- 100*cumsum(v)/sum(v)

Checking the output from OP's method

identical(percovN, percov)
#[1] TRUE

Upvotes: 5

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