r - Extract numeric elements from a vector

Question

I have a vector 'a' which has numeric and non-numeric elements. I want to extract the numeric elements from the vector and build a new vector. How do I do this?

So if a is:

a = c(15, 3, 44, "hello", 4, "NA")

I want to get a vector with four elements namely elements 15 3 44 and 4

Answer 1

b = as.numeric(a)
b = b[!is.na(b)]
b