[R] Optimize a function with Discrete inputs

[R. Michael Weylandt]

On Thu, Aug 2, 2012 at 5:58 AM, loyolite270 <loyolite270 at gmail.com> wrote:
> oh sorry ..
>
> The detailed description of the problem is given below
>
> dataFrame is matrix of dim 100X100 with some values

Odd name for something that's not a dataFrame.... (i.e., data.frame != matrix)

> a is a vector of length 1
> x is a vector of any length between 1 to 99
>
> funcScore<-function(a,x){
>
>     sc<-0
>     sc1<-0
>
>      for(j in 1:(length(x))){
>         sc<-sc+abs(dataFrame[a,x[j]])
>       }
>
>     if(length(x)==1){
>       sc1<-0
>     }
>
>     else{
>        if(length(x)>1){
>           for(i in 1:(length(x)-1)){
>                for(j in (i+1):(length(x))){
>                       sc1 <- sc1+abs(dataFrame[(x[i]-1),x[j]])
>                }
>           }
>        }
>     }
>    score <- sc-sc1
>    return(score)
>  }


Surely you can write this more efficiently:

score <- function(a, x, datfrm){
    sc <- sum(abs(datfrm[a, x]))

    # Something similar for sc1

   sc - sc1
}

Depending on how fast you get it (and I expect massive speed ups upon
rewrite if you vectorize properly), an exhaustive search via combn()
or expand.grid() might work -- otherwise, see combinatorial
optimization pointers, as I noted earlier.

Best,
Michael

>
> Given the value of "a",  i would like to use some optimization function (
> value of x) to maximize the score, such that x can be any combination ?
>
> Thanks
>
>
>
>
>
>
> --
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