Christopher Yau - 11 months ago 33

R Question

I am a beginner in R and am attempting the following question:

Create a function in R which takes as its

input a natural number N and returns as an output the list of

all perfect numbers between 1 and N.

There are 3 steps here:

1. Check the list of factors

2. Check whether it is a perfect number

3.check from 1 to 10000

`factorlist<-function(n){`

if(n<2){return("Invalid Input")}

if(n%%1!=0){return("Invalid Input")}

vec<-0

for(i in 1:(n-1)){

if(n%%i==0){

vec[length(vec)]<-i

vec<-c(vec,0)

}

}

vec<-vec[-length(vec)]

return(vec)

}

perfectcheck<-function(n){

if(n-sum(factorlist(n)) ==0) {return("Perfect Number")}

else{return("Not Perfect Number")}

}

perfectcheckN<-function(N){

for(i in 1:N){

if(perfectcheck(i)=="Perfect Number"){

vec[length(vec)]<-i

vec<-c(vec)

}

}

vec<-vec[-length(vec)]

return(vec)

}

and i got the following error for my third step

`Error in sum(factorlist(n)) : invalid 'type' (character) of argument`

I spent like few hours and still could not figure out my mistake, please help. Thanks!

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Answer Source

The output of `factorlist(i)`

is character when `i==1`

.

There's a lot of loops and ifs in your code. You can just do

```
facs <- function (x) {
x <- as.integer(x)
div <- seq_len(abs(x) - 1L)
div[x%%div == 0L]
}
perfectcheckN <- function(N){
out <- 1:N
out[sapply(out, function(x) x == sum(facs(x)))]
}
```

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