From: Zack Weinberg <zack_at_cogsci.ucsd.edu>

Date: Tue, 22 May 2007 00:13:38 -0700

R-devel_at_r-project.org mailing list

https://stat.ethz.ch/mailman/listinfo/r-devel Received on Tue 22 May 2007 - 09:08:53 GMT

Date: Tue, 22 May 2007 00:13:38 -0700

I have noticed that in R 2.5.0, no method of textual output will print
a "double" mode quantity with more than 15 digits after the decimal
point. From the help page (?print.default) it appears that this is
intentional, since digits after the fifteenth may be uncertain.
However, fifteen digits after the decimal point are not enough to
represent all the values that an IEEE-double can take. (You need one
more.) This means it is now impossible to write out data in textual
format (e.g. in order to manipulate it with another program) and read
back in exactly the same values. Some analyses are sensitive to this
sort of extra rounding, especially if it happens repeatedly.

[Tangentially, support for C99 hexadecimal notation for floating point values in input and output would also be nice, but wouldn't help much for interoperability, since very few programs understand it.]

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https://stat.ethz.ch/mailman/listinfo/r-devel Received on Tue 22 May 2007 - 09:08:53 GMT

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