[R] Problem with products in R ?

[Martin Maechler]

[.....................]

Sorry to prolong this thread,  but I'm a bit astonished.

'bc' has been a really great tool when it was created (1975, at
Bell labs, according to Wikipedia) and made available, open
source, eventually, and I have been fond of it at the time.

On the other hand, we have had the GNU GMP and MPFR C libraries with
state of the art algorithms, in active development, ....
and R packages  'gmp' (for a long time) and 'Rmpfr' for several
years now.

As we are R users as opposed to C programmers (who may be fond
of 'bc' because of its C-like syntax), and of course, as I'm
involved in the maintenance of both R packages 'gmp' and 'Rmpfr',
I wonder why you are not using these which contain considerably
more functionality, notably than the bc interface package.

Martin


    > On Mon, May 5, 2014 at 11:09 PM, Richard M. Heiberger <rmh at temple.edu> wrote:
    >> Gabor,
    >> 
    >> Can you confirm that the bc function is supposed to be current.
    >> The bc package works with my Mac, but not with Windows.
    >> I keep getting the message
    >> 
    >> Error in system(cmd, input = input, intern = TRUE) : -l
    >> 
    >> The FAQ on your https://code.google.com/p/r-bc/ page didn't get me past that
    >> problem.  I tried both the download bc.zip from the page and also the cygwin bc.
    >> 
    >> A secondary issue is that placing your bc.exe into c:/Program
    >> Files/R/R-3.1.0/library/bc/bcdir/bc.exe
    >> gives the message
    >>> one <- bc(1)
    >> Error in system(cmd, input = input, intern = TRUE) :
    >> 'C:/Program' not found
    >> 
    >> Working around that is possible with
    >>> bc.cmd <- "C:/Progra~1/R/R-3.1.0/library/bc/bcdir/bc.exe -l"
    >>> one <- bc(1, cmd=bc.cmd)
    >> but the next line gives the same problem
    >>> one
    >> Error in system(cmd, input = input, intern = TRUE) :
    >> 'C:/Program' not found
    >> 
    >> Thanks
    >> Rich
    >> 
    >> 
    >> On Sun, May 4, 2014 at 1:10 PM, Gabor Grothendieck
    >> <ggrothendieck at gmail.com> wrote:
    >>> Checking this with the bc R package (https://code.google.com/p/r-bc/),
    >>> the Ryacas package (CRAN), the gmp package (CRAN) and the Windows 8.1
    >>> calculator all four give the same result:
    >>> 
    >>>> library(bc)
    >>>> bc("168988580159 * 36662978")
    >>> [1] "6195624596620653502"
    >>> 
    >>>> library(Ryacas)
    >>>> yacas("168988580159 * 36662978", retclass = "character")
    >>> 6195624596620653502
    >>> 
    >>>> library(gmp)
    >>>> as.bigz("168988580159") * as.bigz("36662978")
    >>> Big Integer ('bigz') :
    >>> [1] 6195624596620653502
    >>> 
    >>> 
    >>> On Sun, May 4, 2014 at 12:50 PM, Ted Harding <Ted.Harding at wlandres.net> wrote:
    >>>> On 04-May-2014 14:13:27 Jorge I Velez wrote:
    >>>>> Try
    >>>>> 
    >>>>> options(digits = 22)
    >>>>> 168988580159 * 36662978
    >>>>> # [1] 6195624596620653568
    >>>>> 
    >>>>> HTH,
    >>>>> Jorge.-
    >>>> 
    >>>> Err, not quite ... !
    >>>> I hitch my horses to my plough (with help from R):
    >>>> 
    >>>> options(digits=22)
    >>>> 168988580159*8 = 1351908641272 (copy down)
    >>>> 168988580159*7 = 1182920061113  ( " " )
    >>>> 168988580159*9 = 1520897221431  ( " " )
    >>>> 168988580159*2 =  337977160318  ( " " )
    >>>> 168988580159*6 = 1013931480954  ( " " )^3
    >>>> 168988580159*3 =  506965740477  ( " " )
    >>>> 
    >>>> 1351908641272
    >>>> 11829200611130
    >>>> 152089722143100
    >>>> 337977160318000
    >>>> 10139314809540000
    >>>> 101393148095400000
    >>>> 1013931480954000000
    >>>> 5069657404770000000
    >>>> ======================
    >>>> 6195624596620653502
    >>>> [after adding up mentally]
    >>>> 
    >>>> compared with Jorge's:
    >>>> 6195624596620653568
    >>>> 
    >>>> ("02" vs "68" in the final two digits).
    >>>> 
    >>>> Alternatively, if using a unixoid system with 'bc' present,
    >>>> one can try interfacing R with 'bc'. 'bc' is an calculating
    >>>> engine which works to arbitrary precision.
    >>>> 
    >>>> There certainly used to be a utility in which R can evoke 'bc',
    >>>> into which one can enter a 'bc' command and get the result
    >>>> returned as a string, but I can't seem to find it on CRAN now.
    >>>> In any case, the raw UNIX command line for this calculation
    >>>> with 'bc' (with result) is:
    >>>> 
    >>>> $ bc -l
    >>>> [...]
    >>>> 168988580159 * 36662978
    >>>> 6195624596620653502
    >>>> quit
    >>>> 
    >>>> which agrees with my horse-drawn working.
    >>>> 
    >>>> Best wishes to all,
    >>>> Ted.
    >>>> 
    >>>>> On Sun, May 4, 2014 at 10:44 PM, ARTENTOR Diego Tentor <
    >>>>> diegotentor71 at gmail.com> wrote:
    >>>>> 
>>>>> Trying algorithm for products with large numbers i encountered a difference
>>>>> between result of 168988580159 * 36662978 in my algorithm and r product.
>>>>> The Microsoft calculator confirm my number.
    >>>>>> 
>>>>> Thanks.
>>>>> --
>>>>> *        Gráfica ARTENTOR          *
    >>>>>> 
>>>>> de Diego L. Tentor
>>>>> Echagüe 558
>>>>> Tel.:0343 4310119
>>>>> Paraná - Entre Ríos
    >>>> 
    >>>> -------------------------------------------------
    >>>> E-Mail: (Ted Harding) <Ted.Harding at wlandres.net>
    >>>> Date: 04-May-2014  Time: 17:50:54
    >>>> This message was sent by XFMail
    >>>> 
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    >>> 
    >>> 
    >>> 
    >>> --
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    >>> 
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    > -- 
    > Statistics & Software Consulting
    > GKX Group, GKX Associates Inc.
    > tel: 1-877-GKX-GROUP
    > email: ggrothendieck at gmail.com

    > ______________________________________________
    > R-help at 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.