R help - May 2013 - How many decimal places of information does R actually use in computation?

Dear R-users:

Hi, I read here (
http://stackoverflow.com/questions/2287616/controlling-digits-in-r) that R
is only accurate up to the 15th decimal place, despite the fact that if you
choose to display more decimal places, it will. I wonder if R uses the
information beyond the 15th decimal place in actual computation. Thanks!


Best,
Xiao

	[[alternative HTML version deleted]]

See, e.g.

http://en.wikipedia.org/wiki/Double-precision_floating-point_format

Also in ?print.default  please note:

Large number of digits

Note that for large values of digits, currently for digits >= 16, the
calculation of the number of significant digits will depend on the
platform's internal (C library) implementation of sprintf()
functionality.

-- Bert

On Mon, May 20, 2013 at 6:06 PM, Xiao He <praguewatermelon at gmail.com>
wrote:
> Dear R-users:
>
> Hi, I read here (
> http://stackoverflow.com/questions/2287616/controlling-digits-in-r) that R
> is only accurate up to the 15th decimal place, despite the fact that if you
> choose to display more decimal places, it will. I wonder if R uses the
> information beyond the 15th decimal place in actual computation. Thanks!
>
>
> Best,
> Xiao
>
>         [[alternative HTML version deleted]]
>
> ______________________________________________
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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.


-- 

Bert Gunter
Genentech Nonclinical Biostatistics

Internal Contact Info:
Phone: 467-7374
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