[R] From polynomial to function

Karl Ove Hufthammer karl at huftis.org
Wed Jan 12 10:47:31 CET 2011

Alaios wrote:

> x<-legendre.polynomials(2)[[3]]
>> x
> -0.5 + 1.5*x^2
>> str(x)
> Class 'polynomial'  num [1:3] -0.5 0 1.5
> As you can see from the code above str(x) returns that x is of class
> polynomial. I want to use that polynomial as a function. The reason for
> that is that I would be grateful if I can feed that kind of function
> inside integrate(f,lower=,upper=)

You can use the ‘as.function’ function. But if you’re just going to 
integrate the polynomial anyway, why don’t you just use the ‘integral’ 
function? It’s much more accurate than using numerical integration.

BTW, to see which functions handle ‘polynomial’ objects, use

 [1] as.character.polynomial* as.function.polynomial*  coef.polynomial*        
 [4] deriv.polynomial*        GCD.polynomial*          integral.polynomial*    
 [7] LCM.polynomial*          lines.polynomial*        Math.polynomial*        
[10] Ops.polynomial*          plot.polynomial*         points.polynomial*      
[13] predict.polynomial*      print.polynomial*        solve.polynomial*       
[16] summary.polynomial*      Summary.polynomial*     

Karl Ove Hufthammer

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