www.pudn.com > geometric.rar > ycurve.m, change:2004-08-13,size:2919b


function ynot=ycurve(x,y,xnot)  % ynot=ycurve(x,y,xnot) % % compute the y coordinates of the curve given by x,y at the point xnot. % If the curve is multivalued, then multiple y's will be returned. If the % curve is a polygon, then it must have its first and last points explicitly % equal. If xnot lies outside the bounds and the curve is not a polygon, % then the curve is extrapolated by repeating the% first or last sample as % needed. If it is outside the bounds and the curve is a polygon, then [] % is returned. % % by G.F. Margrave December 1993 % % NOTE: It is illegal for you to use this software for a purpose other % than non-profit education or research UNLESS you are employed by a CREWES % Project sponsor. By using this software, you are agreeing to the terms % detailed in this software's Matlab source file.   % BEGIN TERMS OF USE LICENSE % % This SOFTWARE is maintained by the CREWES Project at the Department % of Geology and Geophysics of the University of Calgary, Calgary, % Alberta, Canada.  The copyright and ownership is jointly held by  % its author (identified above) and the CREWES Project.  The CREWES  % project may be contacted via email at:  crewesinfo@crewes.org %  % The term 'SOFTWARE' refers to the Matlab source code, translations to % any other computer language, or object code % % Terms of use of this SOFTWARE % % 1) Use of this SOFTWARE by any for-profit commercial organization is %    expressly forbidden unless said organization is a CREWES Project %    Sponsor. % % 2) A CREWES Project sponsor may use this SOFTWARE under the terms of the  %    CREWES Project Sponsorship agreement. % % 3) A student or employee of a non-profit educational institution may  %    use this SOFTWARE subject to the following terms and conditions: %    - this SOFTWARE is for teaching or research purposes only. %    - this SOFTWARE may be distributed to other students or researchers  %      provided that these license terms are included. %    - reselling the SOFTWARE, or including it or any portion of it, in any %      software that will be resold is expressly forbidden. %    - transfering the SOFTWARE in any form to a commercial firm or any  %      other for-profit organization is expressly forbidden. % % END TERMS OF USE LICENSE  	ind=find(x==xnot); 	if(isempty(ind)) 		ind=surround(x,xnot); 		if(isempty(ind)) % test for out of range 			if( x(1)==x(length(x)) & y(1)==y(length(y)) ) 				ynot=[]; % don't extrapolate a polygon 				return; 			else 				% extrapolate at constant y either the first or last point 				xends=[x(1) x(length(x))]; 				yends=[y(1) y(length(y))]; 				if( xnot < xends(1) & xnot< xends(2) ) 					ind=find(xends==min(xends)); 					ynot=yends(ind); 					return; 				else 					ind=find(xends==max(xends)); 					ynot=yends(ind); 					return; 				end 			end 		end 				 		ynot=y(ind)-(x(ind)-xnot).*(y(ind)-y(ind+1))./(x(ind)-x(ind+1)); 	else 		ynot=y(ind); 	end