R help - Oct 2011 - converting string fractions to numerics

Dear R People:

Suppose I have the following:

"pi/2"

and I would like it to be 1.57.....

Using as.numeric, here is my result:
> as.numeric("pi/2")
[1] NA
Warning message:
NAs introduced by coercion
>
Is there a way to produce the numeric result, please?

Thanks,
Erin


-- 
Erin Hodgess
Associate Professor
Department of Computer and Mathematical Sciences
University of Houston - Downtown
mailto: erinm.hodgess at gmail.com

I would imagine that you could parse+evaluate it like you asked about on another
thread; this isn't tested though. Does that work in your context?

Michael Weylandt

On Oct 19, 2011, at 2:30 AM, Erin Hodgess <erinm.hodgess at gmail.com>
wrote:
> Dear R People:
> 
> Suppose I have the following:
> 
> "pi/2"
> 
> and I would like it to be 1.57.....
> 
> Using as.numeric, here is my result:
> 
>> as.numeric("pi/2")
> [1] NA
> Warning message:
> NAs introduced by coercion
>> 
> 
> Is there a way to produce the numeric result, please?
> 
> Thanks,
> Erin
> 
> 
> -- 
> Erin Hodgess
> Associate Professor
> Department of Computer and Mathematical Sciences
> University of Houston - Downtown
> mailto: erinm.hodgess at gmail.com
> 
> ______________________________________________
> 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.

Hi,

I believe you want

eval(parse(text="pi/2"))

a word of warning exemplified in

eval(parse(text="library(fortunes) ; fortune(106)"))

HTH,

baptiste



On 19 October 2011 19:30, Erin Hodgess <erinm.hodgess at gmail.com>
wrote:
> Dear R People:
>
> Suppose I have the following:
>
> "pi/2"
>
> and I would like it to be 1.57.....
>
> Using as.numeric, here is my result:
>
>> as.numeric("pi/2")
> [1] NA
> Warning message:
> NAs introduced by coercion
>>
>
> Is there a way to produce the numeric result, please?
>
> Thanks,
> Erin
>
>
> --
> Erin Hodgess
> Associate Professor
> Department of Computer and Mathematical Sciences
> University of Houston - Downtown
> mailto: erinm.hodgess at gmail.com
>
> ______________________________________________
> 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.
>

On 19/10/11 19:30, Erin Hodgess wrote:
> Dear R People:
>
> Suppose I have the following:
>
> "pi/2"
>
> and I would like it to be 1.57.....
>
> Using as.numeric, here is my result:
>
>> as.numeric("pi/2")
> [1] NA
> Warning message:
> NAs introduced by coercion
>>
>
> Is there a way to produce the numeric result, please?
Same answer: parse --- despite what fortune() says.

s <- "pi/2"
eval(parse(text=s))
[1] 1.570796

	cheers,

		Rolf