R help - May 2004 - Problem with 'expression'

DeaR useRs:

Excuses by my English.
I have a problem with 'expression' function.

For example:

	a<-expression(exp(-x^2))
	b<-expression(exp(x^2))

And I want to calculate:

	a*b

And R returns:

	Error in a * b : non-numeric argument to binary operator

I don't know what happend.
Which is the way to making operations with expressions?
Thanks.

On Tue, May 11, 2004 at 04:31:21PM +0200, Perez Martin, Agustin wrote:
> For example:
> 
> 	a<-expression(exp(-x^2))
> 	b<-expression(exp(x^2))
> 
> And I want to calculate:
> 
> 	a*b
Use

t<-2
expression(a, list(x=t))*expression(b, list(x=t))

I am not sure what you are using these for, but maybe you could also
use functions --- more convenient for calculations.  Eg

a <- function(x) { exp(-x^2) }
b <- function(x) { exp(x^2) }
a(x)*b(x) # =1

For evaluating the same functions many times, see ?sapply and the
related pages.

Best,

Tamas

-- 
Tam??s K. Papp
E-mail: tpapp at axelero.hu
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