as.integer(x, ...)
integer(length = 0)
is.integer(x)

`integer`

creates a integer vector of the specified length. Each element of the vector is equal to `0`

.

`as.integer`

attempts to coerce its argument to be of integer type. The answer will be `NA`

unless the coercion succeeds.

`is.integer`

returns `TRUE`

or `FALSE`

depending on whether its argument is of integer type or not,

The weird thing I find when I am trying to use is.integer is, is.integer(3) will return false.

so what happens?

because

Becaues is.integer shows the internal representation, which is not an
integer but a double (real number). Some functions create integer vectors,
for example the : notation:
>* is.integer(1:10) *[1] TRUE
Or, is.integer(as.integer(3)) will also return TURE

Note: `is.integer(x)`

does **not** test if `x`

contains integer numbers! For that, use `round`

, as in the function `is.wholenumber(x)`

in the examples:

is.wholenumber <-
function(x, tol = .Machine$double.eps^0.5) abs(x - round(x)) < tol

To test if a R object contains only integers:

*!any(x!=as.integer(x))*

Reference:

http://127.0.0.1:30947/library/base/html/integer.html

http://tolstoy.newcastle.edu.au/R/help/05/07/7671.html

https://stat.ethz.ch/pipermail/r-help/2006-January/086797.html

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