Follow-up: You can strip the quotation marks from the output, if you want, by wrapping the formatC() command in cat(). Example:
formatC(X,3,format="f") # [1] "1.865" "0.405" "0.147" "1.731" "0.090" cat(formatC(X,3,format="f"),"\n") # 1.865 0.405 0.147 1.731 0.090 Ted. On 28-Apr-10 22:12:56, Ted Harding wrote: > On 28-Apr-10 21:45:12, Steve Taylor wrote: >> >> Is this a bug somewhere? The format function, using a specific >> number of digits, doesn't give sensible results: >> >> R> set.seed(2);print(x<-rexp(5)) >> [1] . >> R> format(x,digits=1) >> [1] "1.87" "0.40" "0.15" "1.73" "0.09" >> R> format(x,digits=2) >> [1] "1.87" "0.40" "0.15" "1.73" "0.09" >> R> format(x,digits=3) >> [1] "1.8654" "0.4047" "0.1467" "1.7307" "0.0895" > > Not a bug (unless you consider the documented behaviour to amount > to a bug)! > > From: ?format > > digits: how many significant digits are to be used for > numeric and complex 'x'. The default, 'NUL'?, uses > 'getOption(digits)'. This is a suggestion: enough > decimal places will be used so that the smallest > (in magnitude) number has this many significant digits, > > And that is exactly what is happening. > > In your first example, the smallest number 0.08953 rounds > (to 1 significant digit) to 0.09 and therefore prints as 0.09. > > In the second, 0.08953 rounds (to 2 significant digits) to 0.090, > which can be printed without further loss of precision as 0.09 > while giving the other numbers 2 significant digits. > > In the third, 0.08953 rounds (to 3 significant digits) to 0895 > The point about the four significant digits given for the > other (larger numbers) is that withg format() *all the numbers > are printed to the same number of decimal places*. Hence the > smallest number gets 3 signficicant digits, hence 4 decimal > places. The other larger numbers will then also get 4. > > It looks as though, lurking behind your question, is a secret > wish for a fixed number of *decimal places* (1, or 2 or 3 in > your examples). For this, try formatC() (but be careful): > > X <- c(1.86535, 0.40475, 0.14665, 1.73071, 0.08953) > formatC(X,2) > # [1] "1.9" "0.4" "0.15" "1.7" "0.09" > formatC(X,2,format="f") > # [1] "1.87" "0.40" "0.15" "1.73" "0.09" > formatC(X,3) > # [1] "1.87" "0.405" "0.147" "1.73" "0.0895" > formatC(X,3,format="f") > # [1] "1.865" "0.405" "0.147" "1.731" "0.090" > > Hoping this helps! > Ted. > > -------------------------------------------------------------------- > E-Mail: (Ted Harding) <ted.hard...@manchester.ac.uk> > Fax-to-email: +44 (0)870 094 0861 > Date: 28-Apr-10 Time: 23:12:53 > ------------------------------ XFMail ------------------------------ -------------------------------------------------------------------- E-Mail: (Ted Harding) <ted.hard...@manchester.ac.uk> Fax-to-email: +44 (0)870 094 0861 Date: 28-Apr-10 Time: 23:20:31 ------------------------------ 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.
