Here's one long-winded way of going about it, using R's ability to
manipulate functions as first class objects:
> f.string
[1] "x1 + sqrt(3*x2)"
> p.string <- parse(text=f.string)
> f <- function() {} # empty function
> v <- all.vars(p.string) # all the variables in the expression
> a <- do.call("alist", as.list(rep(TRUE, length(v)))) # contruct arguments
> names(a) <- v
> formals(f) <- a
> body(f) <- p.string
> f
function (x1 = TRUE, x2 = TRUE)
x1 + sqrt(3 * x2)
> f(3, 4)
[1] 6.464102
Andy
_____
From: [EMAIL PROTECTED] on behalf of Renaud Lancelot
Sent: Sat 7/8/2006 6:25 PM
To: Cleber N.Borges
Cc: r-help@stat.math.ethz.ch
Subject: Re: [R] String mathematical function to R-function [Broadcast]
> fun_String <- "-100*x1 + 0*x2 + 100*x3"
>
> fun <- function(x1, x2, x3){
+ eval(parse(text = fun_String))
+ }
>
> fun(4:0, -2:2, 0:4)
[1] -400 -200 0 200 400
Best,
Renaud
2006/7/8, Cleber N.Borges <[EMAIL PROTECTED]>:
>
>
> hello
>
> I make a subroutine that give-me a (mathematical)
> function in string format.
> I would like transform this string into function ( R
> function ).
>
> thanks for any tips.
> cleber
>
>
> #e.g.
> fun_String = "-100*x1 + 0*x2 + 100*x3"
>
> fun <- function(x1,x2,x3){
> return(
> ############
>
> evaluation( fun_String )
>
> ############
> )
>
>
>
>
>
> True String mathematical function :-( :-(
>
> > nomes
> [1] "8.49*x1*z1 + 6.13*x1*z2 + 6.4*x1*z3 + 6.9*x2*z1 +
> 4.54*x2*z2 + 3.99*x2*z3 + 19.31*x3*z1 + 12.49*x3*z2 +
> 3.86*x3*z3 + 5.25*x1*z1*z2 + -6.2*x1*z1*z3 +
> 9.07*x1*z2*z3 + 10.87*x2*z1*z2 + 9.78*x2*z1*z3 +
> 49.05*x2*z2*z3 + 4.56*x1*x2*z1 + -4.9*x1*x2*z2 +
> 4.01*x1*x2*z3 + -0.39*x3*z1*z2 + 14.34*x3*z1*z3 +
> 0.7*x3*z2*z3 + -2.84*x1*x3*z1 + 20.25*x1*x3*z2 +
> 6.44*x1*x3*z3 + -4.91*x2*x3*z1 + 5.45*x2*x3*z2 +
> 37.99*x2*x3*z3 + -22.24*x1*z1*z2*z3 +
> -97.41*x2*z1*z2*z3 + -8.67*x1*x2*z1*z2 +
> 49.14*x1*x2*z1*z3 + 14.24*x1*x2*z2*z3 +
> 282.71*x3*z1*z2*z3 + 34.83*x1*x3*z1*z2 +
> 111.2*x1*x3*z1*z3 + 101.38*x1*x3*z2*z3 +
> -6.93*x2*x3*z1*z2 + 90.16*x2*x3*z1*z3 +
> -9.11*x2*x3*z2*z3 + 17.22*x1*x2*x3*z1 +
> -29.42*x1*x2*x3*z2 + -19.87*x1*x2*x3*z3 +
> -277.41*x1*x2*z1*z2*z3 + -482.82*x1*x3*z1*z2*z3 +
> -688.23*x2*x3*z1*z2*z3 + -588.4*x1*x2*x3*z1*z2 +
> -197.31*x1*x2*x3*z1*z3 + -722.58*x1*x2*x3*z2*z3 +
> 5536.59*x1*x2*x3*z1*z2*z3"
> >
>
>
>
>
>
> _______________________________________________________
>
> o discador agora!
>
> ______________________________________________
> R-help@stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
<https://stat.ethz.ch/mailman/listinfo/r-help>
> PLEASE do read the posting guide!
http://www.R-project.org/posting-guide.html
<http://www.R-project.org/posting-guide.html>
>
--
Renaud LANCELOT
Département Elevage et Médecine Vétérinaire (EMVT) du CIRAD
Directeur adjoint chargé des affaires scientifiques
CIRAD, Animal Production and Veterinary Medicine Department
Deputy director for scientific affairs
Campus international de Baillarguet
TA 30 / B (Bât. B, Bur. 214)
34398 Montpellier Cedex 5 - France
Tél +33 (0)4 67 59 37 17
Secr. +33 (0)4 67 59 39 04
Fax +33 (0)4 67 59 37 95
______________________________________________
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https://stat.ethz.ch/mailman/listinfo/r-help
<https://stat.ethz.ch/mailman/listinfo/r-help>
PLEASE do read the posting guide!
http://www.R-project.org/posting-guide.html
<http://www.R-project.org/posting-guide.html>
______________________________________________
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PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
