integer

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: "G??ran Brostr??m" <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


 

G??ran Brostr??m 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".]

G??ran,

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

   

G??ran