Kevin -
Read more closely "levels", being an optional vector of the values x
might have taken. You are saying x might have taken 1:20, and then
giving it the first 20 letters, which are not part of "the values x
might have taken".
Try:
x <- factor(letters[1:20])
levels(x)
x
vs.
y <- factor(letters[1:20], levels = letters)
levels(y)
y
vs.
z <- factor(letters[1:20], levels = letters[1:19])
levels(z)
z
That might help show you what's going on?
Best,
Erik Iverson
[EMAIL PROTECTED] wrote:
Doing ?factor I get:
x a vector of data, usually taking a small number of distinct values.
levels an optional vector of the values that x might have taken. The default is the set of values taken by x, sorted into increasing order.
So if I do:
factor(letters[1:20],level=seq(1:20)
[1] <NA> <NA> <NA> <NA> <NA> <NA> <NA> <NA> <NA> <NA> <NA> <NA> <NA> <NA> <NA>
[16] <NA> <NA> <NA> <NA> <NA>
Levels: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
So why all of the NA? What happend to 'a'. 'b', etc.? I was expecting a=1, b=2,
c=3 etc.
I am missing something. Please help with my understanding.
Keviin
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