How to convert from category to numeric in r

Question

Here is my problem:

I have a table with categories and I want to rank them:

category
dog
cat
fish
dog
dog

What I want is to add

Answer 1

I assume that if you write "ranks" you mean ranks. I further assume you want to rank according to number of occurrence.

cats <- factor(c("dog", "cat", "fish", "dog", "dog"))

#see help("rank") for other possibilities to break ties
ranks <- rank(-table(cats), ties.method="first")

DF <- data.frame(category=cats, rank=ranks[as.character(cats)])

print(DF)
#   category rank
# 1      dog    1
# 2      cat    2
# 3     fish    3
# 4      dog    1
# 5      dog    1