On 24-03-2012, at 05:35, Shant Ch wrote:
> Hello all,
>
> I was going to solve (n-m)! * (n-k)! = 0.5 *n! * (n-m-k)!
>
> for m when values of n and k are provided
>
>
> n1<-c(10,13,18,30,60,100,500) # values of n
>
> kx<-seq(1,7,1); # values of k
>
>
> slv2<-lapply(n1,function(n){
>
> slv1<-lapply(kx,function(k){
>
> lhs<-function(m)
> {
> fnk<-factorial(n-m)*factorial(n-k)-
> 0.5*factorial(n-m-k)*factorial(n);
> return(fnk);
> }
> un2<-uniroot(lhs,c(0,n))
> un1<-un2$root/n;
> return(rbind(un1));
> });
> rjbk<-data.frame(do.call(cbind,slv1));
> return(cbind(n,rjbk));
> });
> rj<-data.frame(do.call(rbind,slv2));
> rj
>
> I used the above code, but I am getting this error, can anyone help me with
> this.
>
>
> Error in uniroot(lhs, c(0, n)) : f.upper = f(upper) is NA
> In addition: Warning message:
> In gamma(x + 1) : NaNs produced
>
Don't solve (n-m)! * (n-k)! = 0.5 *n! * (n-m-k)!
but rewrite this to use logarithms.
Use lfactorial instead of factorial to
fnk <- lfactorial(n-m) + lfactorial(n-k)-
(log(0.5) + lfactorial(n-m-k) + lfactorial(n))
You will still get warnings from lfactorial:
In lfactorial(n - m - k) : value out of range in 'lgamma'
but it's up to you to do something about that.
Berend
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