[R] Why is.integer() doesn't work with single values?

[Ott Toomet]

Hi,

On Wed, 29 May 2002, Sven Garbade wrote:

  |Hi all,
  |
  |I don't understand the behavior of is.integer():
  |
  |> x <- integer()
  |> is.integer(x)
  |[1] TRUE
  |> x <- 10
  |> is.integer(x)
  |[1] FALSE

This is OK -- x is now 10 (defaults to float), not any more integer().  Note
that assignment deleted the previous definition.

  |> x <- 1:10
  |> is.integer(x)
  |[1] TRUE

1:10 defaults to an integer vector, so your new vector is (a vector of)
integer(s).

  |Why is.interger() returns FALSE if x has only one element? And how can
  |someone check if x is an integer but contains only one value? (R 1.5.0
  |on Linux i386)

length(x) gives the number of values.  

is.integer() gives the type of argument (the way the argument is presented
in memory).  E.g:

> x <- 10
> is.integer(x)
[1] FALSE
> x == as.integer(x) 
  # use rather abs(x - as.integer(x)) < sqrt(Machine()$double.eps)
  # or something similar.
[1] TRUE
> length(x)
[1] 1

Perhaps it helps.

Ott

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