[R] strange digit switching
Peter Dalgaard
p.dalgaard at biostat.ku.dk
Mon Jun 19 20:17:03 CEST 2006
Hans-Peter <gchappi at gmail.com> writes:
> Hi,
>
> I execute the following code snippet.What I don't understand is, that in the
> first two cases the numbers shown don't correnspondant to the input (though
> I have set the options to show 22 digits). When I assign the third number
> which has one place, the display of the numbers is suddenly correct.
>
> Can anybody explain what happens here?
> (this is just a sample, my real problem lies in numbers that I import from a
> datafile and I don't know how to control them when this switching occurs)
This looks like it is windows specific: digits=22 is interpreted as 17
or so. On Linux (FC5) I see a few more digits, but I still get an
extra decimal in the 3rd case.
This is natural since 0.19... needs one more decimal place to be
represented to N digit accuracy than does 6.94... and 8.34...
> ###########################
> options( digits=22 )
> x <- matrix(NA, 3,1)
> x[1] <- 6.94788635771657950
> x # 6.947886357716580 # DIFFERENT ???
> # NA
> # NA
> x[1] == 6.94788635771657950 # but is the same
>
> x[2] <- 8.34284937565404050
> x # 6.947886357716580 # DIFFERENT ???
> # 8.342849375654041 # DIFFERENT ???
> # NA
> x[1] == 6.94788635771657950 # but is the same
>
> x[3] <- 0.19043842368566377
> x # 6.94788635771657950 # NOW OK!!!
> # 8.34284937565404050 # " "
> # 0.19043842368566377 # " "
> x[1] == 6.94788635771657950 # but is the same
>
>
> ###
> platform i386-pc-mingw32
> arch i386
> os mingw32
> system i386, mingw32
> status
> major 2
> minor 3.1
> year 2006
> month 06
> day 01
> svn rev 38247
> language R
> version.string Version 2.3.1 (2006-06-01)
>
>
> --
> Regards,
> Hans-Peter
>
> [[alternative HTML version deleted]]
>
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--
O__ ---- Peter Dalgaard Øster Farimagsgade 5, Entr.B
c/ /'_ --- Dept. of Biostatistics PO Box 2099, 1014 Cph. K
(*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk) FAX: (+45) 35327907
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