On 06-Jun-08 00:48:50, Peter Dunn wrote: > Hi all > I am not a C programmer, but I am trying to understand formatC to > get consistent printing of reals to a given number of significant > digits. > Can someone please explain this to me? These first three give what > I expect on reading ?formatC: > >> formatC(0.0059999, digits=2,format="fg",flag="#") > [1] "0.0060" >> formatC(0.59999, digits=2,format="fg",flag="#") > [1] "0.60" >> formatC(5.9999, digits=2,format="fg",flag="#") > [1] "6.0" > > This seems consistent with what I read (but perhaps do not > understand) in ?formatC, where I read this: > > digits the desired number of digits after the decimal point > (format = "f") or significant digits (format = "g", = "e" or > = "fg"). > > Since I am using format="fg" and digits=2, so I am expecting two > significant digits to always show, which I have above. So I fail to > understand this: > >> formatC(0.000059999, digits=2,format="fg",flag="#") > [1] "0.00006" >> formatC(0.000059, digits=2, format="fg",flag="#") > [1] "0.000059" > > I was expecting both of these to produce "0.000059". But in the > first case above, I get one significant digit only. > > I'm obviously misunderstanding something; can someone enlighten me? > (No doubt, someone will point out a nuance of the help files I > didn't understand!)
I think that what is happening is that 0.000059999 rounds (to 2 significant digits) to 0.000060 in the first instance, and the "0", not being "significant" (it adds no information to 0.00006), is dropped. > Also, since the above obviously doesn't do what I hoped > (consistently printing two sig figs), could someone also explain > how I can consistently get two significant figures in situation > like above? I don't know! I thought using the "width" parameter might do it, but it does not affect the number of decimal places printed. > Thanks as always. > P. Sorry I coujldn't be more helpful! Ted. -------------------------------------------------------------------- E-Mail: (Ted Harding) <[EMAIL PROTECTED]> Fax-to-email: +44 (0)870 094 0861 Date: 06-Jun-08 Time: 02:18:00 ------------------------------ XFMail ------------------------------ ______________________________________________ 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.
