function X = chisquare_inv(P,V);%CHISQUARE_INV  Inverse of chi-square cumulative distribution function (cdf).%%   X = chisquare_inv(P,V) returns the inverse of chi-square cdf with V%   degrees of freedom at fraction P.%   This means that P*100 percent of the distribution lies between 0 and X.%%   To check, the answer should satisfy:   P==gammainc(X/2,V/2)% Uses FMIN and CHISQUARE_SOLVE%% Written January 1998 by C. Torrence	if (nargin < 2), error('Must input both P and V');, end	if ((1-P) < 1E-4), error('P must be < 0.9999');, end		if ((P==0.95) & (V==2)) % this is a no-brainer		X = 5.9915;		return	end		MINN = 0.01;         % hopefully this is small enough	MAXX = 1;            % actually starts at 10 (see while loop below)	X = 1;	TOLERANCE = 1E-4;    % this should be accurate enough    vers = version;    vers = str2num(vers(1));	while ((X+TOLERANCE) >= MAXX)  % should only need to loop thru once		MAXX = MAXX*10.;% this calculates value for X, NORMALIZED by V% Note: We need two different versions, depending upon the version of Matlab.        if (vers >= 6)            X = fminbnd('chisquare_solve',MINN,MAXX,optimset('TolX',TOLERANCE),P,V);        else    		X = fmin('chisquare_solve',MINN,MAXX,[0,TOLERANCE],P,V);        end		MINN = MAXX;	end		X = X*V;  % put back in the goofy V factor	return% end of code