Talk:Retention uniformity

Calculation

Doesn't seem to add much to the article so moved to talk. RJFJR (talk) 14:25, 28 June 2010 (UTC)

The calculation of the R_U requires some operations and is quite difficult to perform in spreadsheets. The following implementations may help. They take the vector of R_f values, returning the single R_U value.

The R (programming language)/S-PLUS implementation:

ru <- function (x) 
{
        x <- sort(x)
        n <- length(x)
        i <- (1:n)/(n+1)
        s <- sum((x-i)^2)
        ru <- 1-sqrt( (6*(n+1)) / (n*(2*n+1)) * s );
        return(ru);

}

The GNU Octave/Matlab implementation:

function res = ru(x)
	x = sort(x);
	n = length(x);
	i = (1:n)./(n+1);
        s = sum((x-i).^2);
        res = 1-sqrt((6.*(n+1))./(n.*(2.*n+1)).*s);
endfunction

The Scilab implementation:

function res = ru(x)
	x = gsort(x,"g","i");
	n = length(x);
	i = (1:n)./(n+1);
        s = sum((x-i).^2);
        res = 1-sqrt((6.*(n+1))./(n.*(2.*n+1)).*s);
endfunction