R : Int vs Num Anomaly in Vector

Question

I was working my way through a primer on R programming and noticed a slight anomaly :

• x <- c(2,1,1,5) produces a vector of type num
• y <- c(1:5) produces a vector of type int
• z <- c(1.5,2.3) produces a vector of type num

Why does this happen ? What is the fundamental data type in R : is it int or is it num ? What happens if one of the elements in the vector is a float , does the type of the vector become float or is it something else ? What happens when all the elements in the vector are float - why is it still num in that case ?

Answer 1

There are two distinct issue at play:

1. In c(2, 1, 1, 5) you are explicitly creating numeric types. For integer, you would have to use c(2L, 1L, 1L, 5L) as only the suffix L ensures creation of an integer type (or casting via as.integer() etc). But read on ...

2. In c(1:5) a historical override for the : comes into play. Because the usage almost always involves integer sequences, this is what you get: integers.

Both forms are documented, so it is not an anomaly as your question title implies.