[R] rounding down with as.integer

[David Winsemius]

Read the message at the bottom of every message from rhelp.

-- 
David.

On Dec 31, 2014, at 8:09 PM, Zaid Bhatti wrote:

> How can I unsubscribe to not receive loop e mails?
> 
> Sent from my Huawei Mobile
> 
> David Winsemius <dwinsemius at comcast.net> wrote:
> 
> 
> On Dec 31, 2014, at 3:24 PM, Mike Miller wrote:
> 
>> This is probably a FAQ, and I don't really have a question about it, but I just ran across this in something I was working on:
>> 
>>> as.integer(1000*1.003)
>> [1] 1002
>> 
>> I didn't expect it, but maybe I should have.  I guess it's about the machine precision added to the fact that as.integer always rounds down:
>> 
>> 
>>> as.integer(1000*1.003 + 255 * .Machine$double.eps)
>> [1] 1002
>> 
>>> as.integer(1000*1.003 + 256 * .Machine$double.eps)
>> [1] 1003
>> 
>> 
>> This does it right...
>> 
>>> as.integer( round( 1000*1.003 ) )
>> [1] 1003
>> 
>> ...but this seems to always give the same answer and it is a little faster in my application:
>> 
>>> as.integer( 1000*1.003 + .1 )
>> [1] 1003
>> 
>> 
>> FYI - I'm reading in a long vector of numbers from a text file with no more than three digits to the right of the decimal.  I'm converting them to integers and saving them in binary format.
>> 
> 
> So just add 0.0001 or even .0000001 to all of them and coerce to integer.
> 
> 
>> Best,
>> Mike
>> 
>> ______________________________________________
>> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
> 
> David Winsemius
> Alameda, CA, USA
> 
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
> 
> ________________________________
> 
> This e-mail may contain information that is privileged or confidential. If you are not the intended recipient, please delete the e-mail and any attachments and notify us immediately.

David Winsemius
Alameda, CA, USA