function v = lpball_vol(par,x,fracrej,takelog)%LPBALL_VOL Volume L_p ball%%        V = LPBALL_VOL(PAR,X,FRACREJ)%% Compute the volume V of the L_p ball in n-D. The radius is the distance% from the center of the ball to the 1-FRACREJ percentile of dataset X.% The parameter PAR contains the P in the Lp distance and the mean MN:%         PAR = [P MN];%% See also: lpball_dd, lpball_distmean, svdd% Copyright: D.M.J. Tax, D.M.J.Tax@prtools.org% Faculty EWI, Delft University of Technology% P.O. Box 5031, 2600 GA Delft, The Netherlandsif nargin<4	takelog = 1;endif nargin<3	fracrej = 0;end[N,n] = size(x);p = par(1);a = par(2:n+1);a = a(:)';if length(a)~=n	error('Mismatch dim. of x and center a');endgoodp = exp(p);diff = abs(x - repmat(a,N,1)).^goodp;diff = sum(diff,2).^(1/goodp);r = dd_threshold(diff,1-fracrej);if takelog	v = n*log(r) + n*log(2) + n*gammaln(1+1./goodp) - gammaln(1+n./goodp);else	v = ((r*2*gamma(1+1/goodp))^n)/(gamma(1+n/goodp));endreturn