>>>>> "MM" == Martin Maechler <[EMAIL PROTECTED]> >>>>> on Tue, 10 Jun 2008 15:05:05 +0200 writes:
>>>>> "PD" == Peter Dunn <[EMAIL PROTECTED]> >>>>> on Tue, 10 Jun 2008 09:25:07 +1000 writes: PD> Hi all After posting what follows, Duncan Murdoch PD> suggested perhaps a bug in formatC, or an error on PD> documentation. Any comments? I apologize for having slightly misread Peter Dunn's message, and consequently having used the wrong example below. Indeed, Peter's example formatC(0.000059999, digits=2,format="fg",flag="#") *is* misbehaving in dropping the trailing zero, after having used C-level sprintf() as I indicated below, and I'm currently testing a patch to fix this bug. Martin Maechler, ETH Zurich. MM> It could be called a bug in your platform's MM> implementation of the C-library internal sprintf() MM> {to which R's sprintf() is an interface}. MM> Things work okay for me on three different Linux platforms and MM> on Solaris SPARC. MM> More details : MM> formatC(x, digits=2, format="fg", flag = "#") MM> ends up calling MM> sprintf("%#<n>.2g", x) MM> where the <n> is carefully determined from x, MM> in your example MM> sprintf("%#3.2g", 0.005999) MM> For me, this correctly gives >> sprintf("%#3.2g", 0.005999) MM> [1] "0.0060" MM> and I assume that for your platform, it wrongly returns MM> "0.006" instead. MM> Can you confirm? MM> What are the exact platform details? MM> Martin Maechler, ETH Zurich PD> In particular, bug, error or not, any ideas about how I PD> can consistently get two significant figures to print? PD> P. PD> ---------- Original Message ---------- PD> Hi all PD> I am not a C programmer, but I am trying to understand PD> formatC to get consistent printing of reals to a given PD> number of significant digits. PD> Can someone please explain this to me? These first PD> three give what I expect on reading ?formatC: >>> formatC(0.0059999, digits=2,format="fg",flag="#") PD> [1] "0.0060" >>> formatC(0.59999, digits=2,format="fg",flag="#") PD> [1] "0.60" >>> formatC(5.9999, digits=2,format="fg",flag="#") PD> [1] "6.0" PD> This seems consistent with what I read (but perhaps do PD> not understand) in ?formatC, where I read this: PD> digits the desired number of digits after the PD> decimal point (format = "f") or significant digits PD> (format = "g", = "e" or = "fg"). PD> Since I am using format="fg" and digits=2, so I am PD> expecting two significant digits to always show, which I PD> have above. So I fail to understand this: >>> formatC(0.000059999, digits=2,format="fg",flag="#") PD> [1] "0.00006" >>> formatC(0.000059, digits=2, format="fg",flag="#") PD> [1] "0.000059" PD> I was expecting both of these to produce "0.000059". PD> But in the first case above, I get one significant digit PD> only. PD> I'm obviously misunderstanding something; can someone PD> enlighten me? (No doubt, someone will point out a PD> nuance of the help files I didn't understand!) PD> Also, since the above obviously doesn't do what I hoped PD> (consistently printing two sig figs), could someone also PD> explain how I can consistently get two significant PD> figures in situation like above? PD> Thanks as always. PD> P. PD> -- Dr Peter Dunn | dunn <at> usq.edu.au Faculty of PD> Sciences, USQ; http://www.sci.usq.edu.au/staff/dunn PD> Aust. Centre for Sustainable Catchments: PD> www.usq.edu.au/acsc MM> ______________________________________________ MM> R-help@r-project.org mailing list MM> https://stat.ethz.ch/mailman/listinfo/r-help MM> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html MM> 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.