Re: [R] Bug in "is" ?

ctu Wed, 24 Sep 2008 10:03:39 -0700

Hi Keith,

No doubt, 7.0 is integer in math. But if people can write 7 why peopleneed to write 7.0 (I do not see any reason to do this). My point isthat R maybe can do something like S-plus. No point to argue. don'tyou think so?

Thanks
Chunhao





Quoting Keith Jewell <[EMAIL PROTECTED]>:

Have you tried is.integer(7.0) in S-Plus? (I have)
Do you think 7.0 is integer?

IMHO in R there is nothing to be fixed (in this regard) except your
understanding.

This is a computer language, not English; intuition isn't reliable, so we
have help pages.
is.integer(x) is not intended to indicate whether the value of x is a whole
number, it indicates whether x has class "integer".
All objects of class "integer" have whole number values, but not all objects
with whole number values have class "integer".
If you want to know whether a value is a whole number you could try (but
there may be a better way, and beware of computer precision)
x == as.integer(x)

If you want a value to be stored in an object of class "integer" you'd
better say so (using as.integer or L or ...), else how is R to know what you
want? As Martin has pointed out, the system could "guess" based on the
presence or absence of a decimal point; I share his opinion that this would
be a "bad thing".

Nuff said.

Keith J

<[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]

Thank you for all of you. Intuitively, 7 is an integer for people who
live in this planet. It is just very difficult for me to believe that  R
does not think 7 is an integer but 7L is.

is.integer(7)  # R 2.7.2

[1] FALSE
Thus, based on Martin's comments, I try it again on the S-PLUS 8.0 and  it
shows

is.integer(7)   # S-PLUS 8.0

[1] T

Hopefully, someday and someone will fix it therefore, R users don't  need
to use as.integer(7) to tell R that 7 is an integer.

Thanks again
Chunhao


Quoting Martin Maechler <[EMAIL PROTECTED]>:

"KJ" == Keith Jewell <[EMAIL PROTECTED]>
    on Wed, 24 Sep 2008 09:46:08 +0100 writes:


    KJ> "7" is an integer, but it's also a real.
    KJ> In R '?is'  and '?is.integer' are clear that you're testing   the
class(es) of
    KJ> objects, not their values.
    KJ> I can't comment on the relationship with "S Programming"

I can:

In S, and S-plus upto version 3.4,
numeric constants such as '7' where  "double" as they are in R.

Then in S-plus 5.1, they became "integer",
and there were tools so users could change all(!!) their S
scripts to use '7.' instead of '7' in all places where numeric
constants were seen, in order to keep behavior back compatible.

R never made such a step (backwards ;-), and never will,
notably since in R we had introduced the explicit long (= long
integer) constants, using the 'L' suffix,
i.e.,  7L is "integer"
        7 is "double"

Note however that for both, is.numeric(.) is fulfilled and
class(.) and mode(.) return "numeric".
Only typeof(.), storage.mode(.)  or  str(.)
(or functions building on these) tell you the difference.

Martin Maechler, ETH Zurich and R core team

[And, yes, if you think further and are wondering:
 If we'd design things from scratch, we would only have S4
 classes and "double" would be a proper class and
 "numeric" would be the class union of {"integer", "double"}
]


    KJ> <[EMAIL PROTECTED]> wrote in message
    KJ> news:[EMAIL PROTECTED]
    >> This is really bothering me! In the Dr. Venables and Dr.
Ripley's book  "S
    >> Programming" Page 105
    >> shows that
    >>> c(is(10,"integer"),is(10.5,"integer"))
    >> [1] T F
    >>
    >> But I try this in R 2.7.2 it shows
    >>> c(is(10,"integer"),is(10.5,"integer"))
    >> [1] FALSE FALSE
    >> Does anyone know what is going on here?
    >>
    >> Appreciate,
    >> Chunhao
    >>
    >> Quoting Yihui Xie <[EMAIL PROTECTED]>:
    >>
    >>> Yes, everyone will agree "7" is an integer, but I don't think
    >>> computers will agree too :-) R thinks it's a double-precision
number,
    >>> except when you explicitly specify it as an integer (say,
    >>> as.integer()).
    >>>
    >>>> class(7)
    >>> [1] "numeric"
    >>>
    >>>> is.double(7)
    >>> [1] TRUE
    >>>
    >>> Regards,
    >>> Yihui
    >>> --
    >>> Yihui Xie <[EMAIL PROTECTED]>
    >>> Phone: +86-(0)10-82509086 Fax: +86-(0)10-82509086
    >>> Mobile: +86-15810805877
    >>> Homepage: http://www.yihui.name
    >>> School of Statistics, Room 1037, Mingde Main Building,
    >>> Renmin University of China, Beijing, 100872, China
    >>>
    >>>
    >>>
    >>> On Wed, Sep 24, 2008 at 12:40 PM,  <[EMAIL PROTECTED]> wrote:
    >>>> Hi R users
    >>>> Is there anything wrong in "is" function? (R 2.7.2)
    >>>> I believe that everyone will agree that "7" is an integer,
right? but
    >>>> why R
    >>>> shows 7 is not an integer
    >>>>
    >>>>> is.integer(7)
    >>>>
    >>>> [1] FALSE
    >>>>>
    >>>>> is(7,"integer")
    >>>>
    >>>> [1] FALSE
    >>>>>
    >>>>> is(as.integer(7), "integer")
    >>>>
    >>>> [1] TRUE
    >>>>
    >>>> Thank you very much in advance
    >>>> Chunhao

    KJ> ______________________________________________
    KJ> R-help@r-project.org mailing list
    KJ> https://stat.ethz.ch/mailman/listinfo/r-help
    KJ> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
    KJ> and provide commented, minimal, self-contained, reproducible
code.

______________________________________________
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______________________________________________
R-help@r-project.org mailing list
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PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.


______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.


______________________________________________
R-help@r-project.org mailing list
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.

Re: [R] Bug in "is" ?

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