On Sep 26, 2013, at 8:06 AM, Pierrick Bruneau wrote:
Just to add a small note,
sin(pi) is below machine precision :
.Machine$double.eps
[1] 2.220446e-16
(see ?.Machine for exact definition)
-> if myval is bounded to be positive, one safe way of testing
equality to
0 would then be "myval < .Machine$double.eps"
That is a more stringent condition than is applied by `all.equal`
which instead uses .Machine$double.eps^0.5.
--
David.
On Thu, Sep 26, 2013 at 2:48 PM, Suzen, Mehmet <msu...@gmail.com>
wrote:
On 26 September 2013 11:30, Rainer M Krug <rai...@krugs.de> wrote:
Why doesn't return me 0?
It isn't R question at all. You might want to read about representing
real numbers in a computer using floating point
http://en.wikipedia.org/wiki/Floating_point
If you want more precision for some reason, you may want to use Rmpfr
package from CRAN, for example
require(Rmpfr)
pii <- mpfr(pi, 1200)
sin(pii)
1 'mpfr' number of precision 1200 bits
[1]
1.22464679914735317722606593227499799708305390129979194948825771626086960997325810377509325527569013655456428540074414189136673810003656057935764118217436637676835016019778833613838580470703060741630570066750947925902443295873487819032259435513861185501796412843027607796970259523768923503206248925733373776859085615900203929142965774524665617260404787862664073939e-16
| > Is that a Fortune? And, if so, should R be using computers?
Don't blame R for real numbers.
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______________________________________________
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
David Winsemius, MD
Alameda, CA, USA
______________________________________________
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