R help - Nov 2006 - Conversion from expression to numeric

Dear All

I am trying to convert from the type "expression" to the type
"numeric". The following works:
> x <- expression(6.2)
> as.numeric(as.character(x))
[1] 6.2

However, the following does not work:
> x <- expression(62/100)
> as.numeric(as.character(x))
[1] NA
Warning message:
NAs introduced by coercion

Any idea about how to deal with the second case?

Thanks in advance,

Paul

Paul Smith wrote:
>>x <- expression(62/100)
>>as.numeric(as.character(x))
> 
> [1] NA
> Warning message:
> NAs introduced by coercion
> 
> Any idea about how to deal with the second case?
> 
  eval-uate the expression:

  > x <- expression(62/100)
  > eval(x)
  [1] 0.62

Barry

On 11/23/06, Barry Rowlingson <B.Rowlingson at lancaster.ac.uk>
wrote:
> >>x <- expression(62/100)
> >>as.numeric(as.character(x))
> >
> > [1] NA
> > Warning message:
> > NAs introduced by coercion
> >
> > Any idea about how to deal with the second case?
> >
>
>   eval-uate the expression:
>
>   > x <- expression(62/100)
>   > eval(x)
>   [1] 0.62
That is it, Barry. Thanks.

Paul

"Paul Smith" <phhs80 at gmail.com> writes:
> Dear All
> 
> I am trying to convert from the type "expression" to the type
> "numeric". The following works:
> 
> > x <- expression(6.2)
> > as.numeric(as.character(x))
> [1] 6.2
> 
> However, the following does not work:
> 
> > x <- expression(62/100)
> > as.numeric(as.character(x))
> [1] NA
> Warning message:
> NAs introduced by coercion
> 
> Any idea about how to deal with the second case?
Well, you could start by watching where you are going...
> x <- expression(62/100)
> x
expression(62/100)
> as.character(x)
[1] "62/100"

and as.numeric wouldn't know dashes about strings that contain
slashes...

eval(x) might be closer to the mark.

-- 
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