向量的对象转换

Question

I run given code:

> mean(as.numeric(x <- 1:4))
[1] 2.5
> class(x)
[1] "integer"
> 
> x <- 2:5
> class(x)
[1] "integer"
> as.numeric(x)
[1] 2 3 4 5
> class(x)
[1] "integer"
> 

Query - As far as I have studied for an object to behave like an integer it has to be assigned L in the end, but over here, I see completely a different story. So, why the classes of x and y are not numeric ?

However, without vector things go as usual:

> a <-3
> class(a)
[1] "numeric"
> b <- 3L
> class(b)
[1] "integer"

Answer 1

If we check the ?":" , it is already described

For numeric arguments, a numeric vector. This will be of type integer if from is integer-valued and the result is representable in the R integer type, otherwise of type "double" (aka mode "numeric").

Here, 2 and 5 are integers and so the sequence will also be integer call. Of course type promotion is there in dynamic languages as opposed to static languages

Also, check the output of

class(seq(2, 5))
#[1] "integer"
class(seq(2.0, 5.0))
#[1] "integer"
class(seq(2.0, 5.0, by = 1.0))
#[1] "numeric"
class(seq(2, 5, by = 1.0))
#[1] "numeric"
class(seq(2, 5, by = 1))
#[1] "numeric"
class(seq(2, 5, by = 1L))
#[1] "numeric"