How to check if a variable is categorical with R?

Question

I have an R data frame , and some of the variables are categorical. For example, sex is “man” or “woman,” and “you smoke” is 0 or 1. Other variables are continuous instead. I would like to know if there is a way to decide whether a variable is categorical or not, and if its frequencies are calculated.

I think in my case a good test would be to check if a variable accepts less than k = 4.

Answer 1

While you should use factors for categorical variables, you can find unique values ​​in the vector xwith uniqueand calculate them:

length(unique(x))