S.Galleg - 1 year ago 136
R Question

# Using for loop in r to get a cumulative sum

I need to solve for the sum of (10^2 + 10^3) 99 cumulative times, so the sum of (1100+1100+1100...(99 times))=Total. I know most people don't like loops but I need to solve for this using a for loop. Here is what I have so far...

``````prob1 <- function(n){
total <- 1100
for(i in 2:99)
total[i] <- sum(i^2 + i^3)
return(total)
}
``````

This is what I get

``````[1]   1100     12     36     80    150    252    392    576    810   1100   1452   1872   2366   2940   3600
[16]   4352   5202   6156   7220   8400   9702  11132  12696  14400  16250  18252  20412  22736  25230  27900
[31]  30752  33792  37026  40460  44100  47952  52022  56316  60840  65600  70602  75852  81356  87120  93150
[46]  99452 106032 112896 120050 127500 135252 143312 151686 160380 169400 178752 188442 198476 208860 219600
[61] 230702 242172 254016 266240 278850 291852 305252 319056 333270 347900 362952 378432 394346 410700 427500
[76] 444752 462462 480636 499280 518400 538002 558092 578676 599760 621350 643452 666072 689216 712890 737100
[91] 761852 787152 813006 839420 866400 893952 922082 950796 980100
``````

How can I get it to add correctly and return just the total?
The total should be 108,900 (I believe)

I looked at your loop issue a little differently since you just wanted the total. Your code was adding elements to a vector with the total[i]. You instead want to just have i be an iterator for adding a number to another number. I initialized that to 0 with the first line.

``````total=0
for (i in 1:99) {
total<-total+(10^2 + 10^3)
i=i+1
}
total
``````

[1] 108900

``````1100*99
``````

[1] 108900

Recommended from our users: Dynamic Network Monitoring from WhatsUp Gold from IPSwitch. Free Download