[Rd] Commas in formatC

Jonathan Rougier J.C.Rougier@durham.ac.uk
Fri, 22 Mar 2002 08:13:57 +0000

Martin Maechler wrote:
> >>>>> "DavidB" == David Brahm <brahm@alum.mit.edu> writes:
>     DavidB> formatC() is great for formatting numbers!  But it
>     DavidB> would be even better if it could optionally insert
>     DavidB> commas (or semicolons), e.g.
>     R> formatC(1234567.89, digits=2, format="f", commas=T)
>     DavidB> [1] "1,234,567.89"
>     DavidB> Here's a snippet of code that does that, which could
>     DavidB> more or less just be inserted into at the end of
>     DavidB> formatC if any R-core guru were so inclined.  "r" is
>     DavidB> the result so far, and "commas" is a logical flag:
>     DavidB> stp <- regexpr("[0-9]+", r);  len <- attr(stp, "match.length")
>     DavidB> if (commas && (maxl <- max(len)) > 3) for (i in seq(3, maxl-1, 3))
>     DavidB> r[len>i] <- paste(substring(r[len>i], 1, (stp+len-1-i)[len>i]),
>     DavidB> substring(r[len>i], (stp+len-i)[len>i]), sep=",")
> Thank you, David, for the suggestion.
> I'm looking at adding something quite a bit more general
> to both format.default() and formatC(), using a new function
> prettyNum() and using new arguments (that are compatible to S-plus'
> format.default).

Hi Martin,

Maybe this is a step in the wrong direction, but I actually like using C
string formatting, eg I would like to be able to type something like

  str <- stringC("The man called %s is %i feet tall", "Sven", 6)

which is also used in Python via the string formatting operator, '%'. 
Is this a possibility?

Cheers, Jonathan.

Jonathan Rougier                       Science Laboratories
Department of Mathematical Sciences    South Road
University of Durham                   Durham DH1 3LE
tel: +44 (0)191 374 2361, fax: +44 (0)191 374 7388
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