R summation of a serie with subscript

Question

I thought it should be an easy one but I have been scratching my head and couldn't find the correct way.

I would like to calculate a summation of series A:

A<-*summation((i=2 to i=s)*K(c1+c2(i-1)))

where k, c1 & c2 are fixed values.

Expand A, i would like to get the sum of all these:

K(c1+c2(2-1))+K(c1+c2(3-1))+.......K(c1+c2(s-1))

To do that in R, here is what I wrote:

A<-function(s){
    for (i in 2:s){
    c1=5
    c2=13.6
    k=10
    sum(k*(c1+c2*(i-1)))
}}

but when I do

A(5)

it didn't come up with anything

So I modified the function and asked it to print what it did:

A<-function(s){
    for (i in 2:s){
    c1=5
    c2=13.6
    k=10
    a<-sum(k*(c1+c2*(i-1)))
    print(a)
}}

> A(5)
[1] 186
[1] 322
[1] 458
[1] 594

Apparently it didn't "sum" all of them but calculated them independently.

So what exactly is the correct codes for summation?

Thanks.

I'm worried. Very worried ... that you think the "(n)" form is somehow connected with picking the n-th item from a vector of value. In R that is done with "[n]" and not "(n)". — IRTFM, May 04 '13 at 01:51

score 3 · Answer 1 · answered May 03 '13 at 21:53

3

Perhaps like this:

K <- 10
c1 <- 5
c2 <- 13.6

sum(K * (c1 + (c2 * (1:4))))

answered May 03 '13 at 21:53

joran

1 Answers1