Hello everyone
On 1 Sep 2007, at 01:39, Duncan Murdoch wrote:
> The IEEE floating point standard allows for negative zero, but it's
> hard
> to know that you have one in R. One reliable test is to take the
> reciprocal. For example,
>
>> y <- 0
>> 1/y
> [1] Inf
>> y <- -y
>> 1/y
> [1] -Inf
On Sat, Sep 01, 2007 at 05:22:26PM -0600, Tony Plate wrote:
> One place where I've been caught by -ve zeros is with unit tests. If
> identical(-0, 0) returns FALSE, and the object storage doesn't preserve
> -ve zeros, that can lead to test failures that are tricky to debug.
>
> However, it does
One place where I've been caught by -ve zeros is with unit tests. If
identical(-0, 0) returns FALSE, and the object storage doesn't preserve
-ve zeros, that can lead to test failures that are tricky to debug.
However, it doesn't look like that is too much a problem in the current
incarnation o
On Fri, Aug 31, 2007 at 08:39:02PM -0400, Duncan Murdoch wrote:
[snip]
> The other day I came across one in complex numbers, and it took me a
> while to figure out that negative zero was what was happening:
>
> > x <- complex(real = -1)
> > x
> [1] -1+0i
> > 1/x
> [1] -1+0i
> > x^(1/3)
>
[EMAIL PROTECTED] wrote:
>
> On 8/31/07, Duncan Murdoch <[EMAIL PROTECTED]> wrote:
>> The IEEE floating point standard allows for negative zero, but it's hard
>> to know that you have one in R. One reliable test is to take the
>> reciprocal. For example,
>>
>> > y <- 0
>> > 1/y
>> [1] Inf
>>
On 8/31/07, Duncan Murdoch <[EMAIL PROTECTED]> wrote:
> The IEEE floating point standard allows for negative zero, but it's hard
> to know that you have one in R. One reliable test is to take the
> reciprocal. For example,
>
> > y <- 0
> > 1/y
> [1] Inf
> > y <- -y
> > 1/y
> [1] -Inf
>
>
Seems the same on this Apple Mac OSX platform:
> y <- 0
> 1/y
[1] Inf
> y <- -y
> 1/y
[1] -Inf
> x <- complex(real = -1)
> x
[1] -1+0i
> 1/x
[1] -1+0i
> x^(1/3)
[1] 0.5+0.8660254i
> (1/x)^(1/3)
[1] 0.5-0.8660254i
> sessionInfo()
R version 2.5.1 (2007-06-27)
powerpc-apple-darwin8.9.1
locale:
en
On 8/31/07, Duncan Murdoch <[EMAIL PROTECTED]> wrote:
> The IEEE floating point standard allows for negative zero, but it's hard
> to know that you have one in R. One reliable test is to take the
> reciprocal. For example,
>
> > y <- 0
> > 1/y
> [1] Inf
> > y <- -y
> > 1/y
> [1] -Inf
>
> The
