How can I use `for loop` at once without non-numeric errors?

October 22, 2022

I wonder how for loop can be used at once without non-numeric error. I would like to make multiple character values in a vector Nums, using for loop.

But after the third line, the vector becomes chr so cannot continue the rest. This comes out to be same even when I use if loop or while loop… Can someone give a hint about this?

  for(n in 1:30){
    Nums<-1:n
    Nums[Nums%%2==0 & Nums%%3==0]<-"OK1"
    Nums[Nums%%2==0 & Nums%%3!=0]<-"OK2"
    Nums[Nums%%2!=0 & Nums%%3==0]<-"OK3"
    Nums[Nums%%2!=0 & Nums%%3!=0]<-n
  }

Error in Nums%%2 : non-numeric argument to binary operator

>Solution :

Character and numeric values can’t coexist in a vector^*. As @Ands. points out, you don’t really need a loop for this. If you want to avoid case_when (which is from the dplyr package, part of the "tidyverse"), you can do:

n <- 30
Nums <- 1:n
x <- as.character(Nums)
x[Nums%%2==0 & Nums%%3==0]<-"OK1"
x[Nums%%2==0 & Nums%%3!=0]<-"OK2"
x[Nums%%2!=0 & Nums%%3==0]<-"OK3"

You don’t need the final statement because the remaining elements were already set to the corresponding numeric values.

If you want to use a for loop and replace as you go, you could convert the vector to a list:

Nums <- 1:n
Nums <- as.list(Nums)
for (i in 1:n) {
   if (i%%2==0 & i%%3==0) Nums[[i]] <- "OK1"
   if (i%%2==0 & i%%3!=0) Nums[[i]] <- "OK2"
   if (i%%2!=0 & i%%3==0) Nums[[i]] <- "OK3"
}
unlist(Nums)

^* Technically they can’t coexist in an atomic vector — lists are vectors too …