[R] integer

[Ludovic Tambour]

Sorry, the formulation of my question is bad. I hope that you have not lost
your time. The problem is not a problem of integer identification.

The problem is :
" I have a numerical function y = f(x1,x2,x3) where x1...x3 are integers. I
would like to determine x1,x2,x3 so that "y" has a minimal value. I know
that
R can determine a minimal value when x1,x2,x3 are real. Is-it possible to do
this when x1, x2, x3 are restricted to be integers ? "

Ludo




----- Original Message -----
From: "Uwe Ligges" <ligges at statistik.uni-dortmund.de>
To: "Göran Broström" <gb at stat.umu.se>
Cc: <r-help at stat.math.ethz.ch>
Sent: Tuesday, November 02, 2004 3:44 PM
Subject: Re: [R] integer


> Göran Broström wrote:
>
> > On Tue, Nov 02, 2004 at 11:36:27AM +0100, Uwe Ligges wrote:
> >
> >>Ludovic Tambour wrote:
> >>
> >>
> >>>Hello,
> >>>
> >>>I need to use "R" to determine parameters which are integers. How I can
do
> >>>this, please ?
> >>
> >>What so you mean with "parameters"? In which context?
> >>
> >>To check whether a numeric vector "x" contains only integers, you can
try
> >>
> >>all.equal(as.integer(x), x)
> >
> >
> > I don't think so:
> >
> >
> >>x <- as.double(c(1, 2))
> >>y <- as.integer(c(1, 2))
> >>all.equal(x, y)
> >
> > [1] TRUE
> >
> > But,
> >
> >
> >>identical(x, y)
> >
> > [1] FALSE
>
> [The story was completely different from the stuff I guessed, so all
> further communication related to this thread is "academic".]
>
> Göran,
>
> yes, as expected.
>
>
> > On the other hand, why not use
> >
> >
> >>is.integer(x)
> >
> > [1] FALSE
> >
> >>is.integer(y)
> >
> > [1] TRUE
> >
> > because I think that a numeric vector can't have a mix of integer and
> > non-integer elements. With a list it's a different story.
>
> Yes.
>
> My guees was that the asker tried to identify integers such as 2, 3 in
> contrast to 2.1, 3.1, ...and you won't know it by looking at R's storage
> mode (my guess was that the asker was not interested in the storage
> mode, but in the nature of the numbers!).
> Note that is.integer(1) is FALSE!!!
>
> The given usage of all.equal() helps to identify 1 as an integer, but
> not 1.1...
>
> Uwe
>
> > Göran
>
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