R Programming error in fert

Question

I am new to R. I'm facing a problem when I do the following:

fert <- as.factor(c(50,20,10,10,20,50))
levels(fert)

This is what I get and it makes sense to me:

[1] "10" "20" "50"

When I run this:

levels(fert)[fert]

I get this:

"50" "20" "10" "10" "20" "50"

I don't understand what this is, I thought it was the definition of fert.

Answer 1

You're using a factor:

fert <-  factor(c(50,20,10,10,20,50))
levels(fert)
#[1] "10" "20" "50"

Factors are always in a sequential form with labels:

as.numeric(fert)
#[1] 3  2  1  1  2  3
#  corresponding to the labels of:
#   50 20 10 10 20 50

That's why:

levels(fert)[c(3,2,1,1,2,3)]
#[1] "50" "20" "10" "10" "20" "50"

You get this:

levels(fert)[fert]
#[1] "50" "20" "10" "10" "20" "50"