[Rd] bug in modulus operator %% (PR#7852)
Duncan Murdoch
murdoch at stats.uwo.ca
Wed May 11 23:27:07 CEST 2005
Robert.McGehee at geodecapital.com wrote:
> Yes, you are correct. I had only checked one of my platforms. Linux
> works as you suggest. But for me on Windows,=20
Certainly looks like a bug on Windows to me. I'm going offline for a
day very soon now, but I'll try to remember to look into it.
Duncan Murdoch
>
>
>>x <- 1
>>y <- 0.2
>>x %/% y
>
> [1] 5 ## I get a 4 in Linux
>
> version
> _ =20
> platform i386-pc-mingw32
> arch i386 =20
> os mingw32 =20
> system i386, mingw32 =20
> status =20
> major 2 =20
> minor 1.0 =20
> year 2005 =20
> month 04 =20
> day 18 =20
> language R =20
>
>
> -----Original Message-----
> From: Peter Dalgaard [mailto:p.dalgaard at biostat.ku.dk]=20
> Sent: Wednesday, May 11, 2005 4:14 PM
> To: McGehee, Robert
> Cc: ted.harding at nessie.mcc.ac.uk; Peter Dalgaard; R-bugs at biostat.ku.dk;
> kjetil at acelerate.com; r-devel at stat.math.ethz.ch
> Subject: Re: [Rd] bug in modulus operator %% (PR#7852)
>
>
> "McGehee, Robert" <Robert.McGehee at geodecapital.com> writes:
>
>
>>Yes, but from ?"%%":
>>"It is guaranteed that 'x =3D=3D (x %% y) + y * (x %/% y)' (up to =
>
> rounding
>
>>error) ..."
>>=20
>>(R 2.1.0)
>>
>>>x <- 1
>>>y <- 0.2
>>>x %% y
>>
>>[1] 0.2
>>
>>>(x %% y) + y * (x %/% y)
>>
>>[1] 1.2
>>=20
>>Certainly 1 does not equal 1.2 as the documentation would suggest, and
>>these seem like large enough numbers to not be effected by rounding
>>errors or lack of precision.
>
>
> Now that looks a bit odd, but it isn't universal:
>
>
>>x <- 1
>>y <- 0.2
>>x %% y
>
> [1] 0.2
>
>>x %/% y
>
> [1] 4
>
>>(x %% y) + y * (x %/% y)
>
> [1] 1
>
> So what platform was that happening on?
>
> --=20
> O__ ---- Peter Dalgaard Blegdamsvej 3 =20
> c/ /'_ --- Dept. of Biostatistics 2200 Cph. N =20
> (*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918
> ~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk) FAX: (+45) 35327907
>
> ______________________________________________
> R-devel at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel
More information about the R-devel
mailing list