[R] more on vectoring a simple for

[Ray Brownrigg]

> Excuse me, but I wasn't clear. It's a generic funcion, like
> f(beta) and g(beta)
> 
> result<-rep(0,3)
> for(i in 1:3) result[i]<-sum(f(beta[-i])/g(beta[-i]))
> 
> for example, f(beta)=log(abs(beta)) and g(beta)=beta^2:
> for(i in 1:3) result[i]<-sum(log(abs(beta[-i]))/(beta[-i]^2))
> 
> How can I write this with no for?
> 
The same principle applies, as long as f() and g() are vector functions.

i.e. sum(F(beta[-i])) = sum(F(beta)) - F(beta[i])
where F() = f()/g()

Viz:
> result <- rep(0, 3)
> beta <- 1:3
> for(i in 1:3) result[i] <- sum(log(abs(beta[-i]))/(beta[-i]^2))
> result
[1] 0.2953548 0.1220680 0.1732868
> sum(log(abs(beta))/(beta^2)) - log(abs(beta))/(beta^2)
[1] 0.2953548 0.1220680 0.1732868
>

Ray
-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-
r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html
Send "info", "help", or "[un]subscribe"
(in the "body", not the subject !)  To: r-help-request at stat.math.ethz.ch
_._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._