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