R help - Nov 2007 - as.character(seq(-.35,.95,.1))

> as.character(seq(-.25,.95,.1))
  [1] "-0.25" "-0.15" "-0.05" "0.05" 
"0.15"  "0.25"  "0.35"  "0.45"
"0.55"  "0.65"  "0.75"  "0.85" 
"0.95"

 > as.character(seq(-.35,.95,.1))
  [1] "-0.35"               "-0.25"                
"-0.15"               "-0.0499999999999999" "0.05"
  [6] "0.15"                "0.25"                 
"0.35"                "0.45"                "0.55"
[11] "0.65"                "0.75"                 
"0.85"                "0.95"

Not a big deal, just curiosity:
Why do I obtain this "ugly" "-0.0499999999999999" instead of
the
expected "-0.05" ?

Regards
K.

see FAQ 7.31

On Nov 20, 2007 10:50 AM, Ken Fullish <ken.mailinglist at mac.com>
wrote:
>
>  > as.character(seq(-.25,.95,.1))
>  [1] "-0.25" "-0.15" "-0.05" "0.05"
"0.15"  "0.25"  "0.35"  "0.45"
> "0.55"  "0.65"  "0.75"  "0.85" 
"0.95"
>
>  > as.character(seq(-.35,.95,.1))
>  [1] "-0.35"               "-0.25"
> "-0.15"               "-0.0499999999999999"
"0.05"
>  [6] "0.15"                "0.25"
> "0.35"                "0.45"               
"0.55"
> [11] "0.65"                "0.75"
> "0.85"                "0.95"
>
> Not a big deal, just curiosity:
> Why do I obtain this "ugly" "-0.0499999999999999"
instead of the
> expected "-0.05" ?
>
> Regards
> K.
>
> ______________________________________________
> R-help at r-project.org mailing list
> 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.
>


-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem you are trying to solve?

On 11/20/2007 10:50 AM, Ken Fullish wrote:
>  > as.character(seq(-.25,.95,.1))
>   [1] "-0.25" "-0.15" "-0.05"
"0.05"  "0.15"  "0.25"  "0.35" 
"0.45"
> "0.55"  "0.65"  "0.75"  "0.85" 
"0.95"
> 
>  > as.character(seq(-.35,.95,.1))
>   [1] "-0.35"               "-0.25"                
> "-0.15"               "-0.0499999999999999"
"0.05"
>   [6] "0.15"                "0.25"                 
> "0.35"                "0.45"               
"0.55"
> [11] "0.65"                "0.75"                 
> "0.85"                "0.95"
> 
> Not a big deal, just curiosity:
> Why do I obtain this "ugly" "-0.0499999999999999"
instead of the
> expected "-0.05" ?
Because as.character() tries to do an accurate conversion, and the 
number in your vector is closer to -0.0499999999999999 than to -0.05.
You could get the "-0.05" by something like round( seq(...), 2).

The reason seq() doesn't give you exactly -0.05 is that the starting 
values and step size you've chosen are not exactly representable in R's 
floating point format.   It can only store fractions exactly when the 
denominator is a power of 2.

Duncan Murdoch