[R] Unexpected behaviour when using format(x, scientific = TRUE) on integer vector

[Bert Gunter]

The behavior is **as documented on the man page**, always the first thing
you should consult. It can be terse, but almost always accurate once
deciphered.
In this case, ?format says for the "scientific" parameter(Highlighting
added):

scientific
Either a logical specifying whether elements of a **real or complex
vector** should be encoded in scientific format, or an integer penalty (see
options("scipen")). Missing values correspond to the current default
penalty.

Your vector is integer, right? The options("scipen") man page also
indicates that fixed format will be used.


Cheers,
Bert

Bert Gunter

"The trouble with having an open mind is that people keep coming along and
sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )


On Sat, Jun 19, 2021 at 9:50 AM Remo Röthlin <avelarius using gmail.com> wrote:

> Dear useRs
>
> I’m encountering an unexpected behaviour when trying to apply format(x,
> scientific = TRUE) on integer vectors (but not double vectors).
> The resulting string is not formatted in scientific notation, however,
> using formatC() instead, the result is as expected.
>
> Is this the expected behaviour of format(x, scientific = TRUE)? I haven’t
> found any information or discussion on a difference in scientific notation
> between format and formatC.
>
> Both functions are implemented as .Internal() functions in C, and while
> do_formatC() uses C’s directly built-in capabilities to format, do_format()
> does additional work.
> Unfortunately my knowledge of R internals is not good enough to see why
> format() treats integers differently in this case.
>
> Warm regards,
>
> Remo
>
> SessionInfo and code to reproduce the issue with output (was also
> reproduced on Windows 10 x64 R 4.1.0 and RStudio Cloud R 3.6.3 & R 4.0.3):
>
> > sessionInfo()
> R version 4.1.0 (2021-05-18)
> Platform: x86_64-apple-darwin17.0 (64-bit)
> Running under: macOS Big Sur 10.16
>
> Matrix products: default
> BLAS:
>  /Library/Frameworks/R.framework/Versions/4.1/Resources/lib/libRblas.dylib
> LAPACK:
> /Library/Frameworks/R.framework/Versions/4.1/Resources/lib/libRlapack.dylib
>
> locale:
> [1] de_CH.UTF-8/de_CH.UTF-8/de_CH.UTF-8/C/de_CH.UTF-8/de_CH.UTF-8
>
> attached base packages:
> [1] stats     graphics  grDevices utils     datasets  methods   base
>
> loaded via a namespace (and not attached):
> [1] compiler_4.1.0
> > Sys.getlocale()
> [1] "de_CH.UTF-8/de_CH.UTF-8/de_CH.UTF-8/C/de_CH.UTF-8/de_CH.UTF-8"
> >
> > numvec <- c(-1.23e4, 1.23e4)
> > typeof(numvec) # double
> [1] "double"
> >
> > intvec <- c(-1.23e4L, 1.23e4L)
> > typeof(intvec) # integer
> [1] "integer"
> >
> > numvec2 <- as.double(intvec)
> > identical(numvec, numvec2)
> [1] TRUE
> >
> > formatC(numvec, format = "e") # Formatted as scientific notation
> [1] "-1.2300e+04" "1.2300e+04"
> > format(numvec, scientific = TRUE) # Formatted as scientific notation
> [1] "-1.23e+04" " 1.23e+04"
> >
> > formatC(intvec, format = "e") # Formatted as scientific notation
> [1] "-1.2300e+04" "1.2300e+04"
> > format(intvec, scientific = TRUE) # *Not* formatted as scientific
> notation
> [1] "-12300" " 12300"
> >
> > formatC(numvec2, format = "e") # Formatted as scientific notation
> [1] "-1.2300e+04" "1.2300e+04"
> > format(numvec2, scientific = TRUE) # Formatted as scientific notation
> [1] "-1.23e+04" " 1.23e+04"
>
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