From: Uwe Ligges <ligges_at_statistik.uni-dortmund.de>

Date: Tue, 22 May 2007 12:10:39 +0200

R-devel_at_r-project.org mailing list

https://stat.ethz.ch/mailman/listinfo/r-devel Received on Tue 22 May 2007 - 10:25:18 GMT

Date: Tue, 22 May 2007 12:10:39 +0200

Zack Weinberg wrote:

> 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.
**>
**> I'd really appreciate some way of forcing R to print enough digits to
**> represent every possible IEEE double value. I would also argue that
**> this should be the default behavior of dump(), write.table() and
**> friends, and save(...,ascii=TRUE), to prevent data loss.
*

formatC(exp(1), digits=100, width=-1)

Uwe Ligges

> [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.]
**>
**> zw
**>
**> ______________________________________________
**> R-devel_at_r-project.org mailing list
**> https://stat.ethz.ch/mailman/listinfo/r-devel
*

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https://stat.ethz.ch/mailman/listinfo/r-devel Received on Tue 22 May 2007 - 10:25:18 GMT

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