How to check if each element in a vector is integer or not in R?

Question

Say, I have a vector y, and I want to check if each element in y is integer or not, and if not, stop with an error message. I tried is.integer(y), but it does not work.

Answer 1

Here's another way (using the same trick as Justin of comparing each number to that number coerced into the 'integer' type):

R> v1 = c(1,2,3)
R> v2 = c(1,2,3.5)
R> sapply(v1, function(i) i == as.integer(i))
[1] TRUE TRUE TRUE
R> sapply(v2, function(i) i == as.integer(i))
[1]  TRUE  TRUE FALSE

To make your test:

R> all(sapply(v2, function(i) i == as.integer(i)))
[1] FALSE