[R] Re: trailing zeroes
Martin Maechler
maechler at stat.math.ethz.ch
Sun Feb 28 01:07:14 CET 1999
>>>>> "BDR" == Prof Brian Ripley <ripley at stats.ox.ac.uk> writes:
>> Date: Fri, 26 Feb 1999 09:59:39 +0000 From: Bendix Carstensen
>> <bxc at svs.dk>
>> When you require 2 digits you expect to find 5.96 printed
BDR> Correction, _you_ expect! Very few computer programs do that.
BDR> You cannot `require' two digits by options(digits=2): ?options
BDR> says
BDR> digits: controls the number of digits to print when print- ing
BDR> numeric values. It is a suggestion only.
>> as 6.0, i.e. a number somewhere between 5.95 and 6.04999999999999.
>> This is apparently not always the case for R. Why does 0 have a
>> special status as trailing digit?
>>
>> > options(digits=2) > x <- c(59.6,59.4) > x [1] 60 59 > x/10 [1] 6.0
>> 5.9 > x[1]/10 [1] 6
BDR> Because that is how the ASCII C printing functions work.
BDR> Ultimately print() calls sprintf with a %x.yf format. What happens
BDR> depends on how that is implemented on your system.
BDR> S-PLUS has an option nsmall to format to do precisely this, and
BDR> there was a question asking how to do it on s-news today. I have
BDR> thought for a while that we need to implement something like this
BDR> in R: maybe I had better do it....
Is it necessary?
In R, we've always been having formatC(.) as an alternative to format(.)
allowing more precise formatting specifications.
However, maybe I didn't understand what yuo were alluding to..
Martin
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