www.pudn.com > geometric.rar > xy2arclen.m, change:2004-08-13,size:3542b

function a=xy2arclen(x,y,xnot,ynot)  % a=xy2arclen(x,y,xnot,ynot) % a=xy2arclen(x,y,xnot) % a=xy2arclen(x,y) % % Given a piecewise linear curve whose nodes are specified by the vectors x & y % XY2ARCLEN, in the form a=xy2arclen(x,y,xnot,ynot), computes the arclength  % (or inline distance) from (x(1),y(1)) to each of the points given by the  % vectors (xnot,ynot). If (xnot,ynot) does not lie on the curve then a NAN  % is returned. In the form, a=xy2arclen(x,y), the arclength to each of the % verticies of (x,y) is returned. Lastly, in the form a=xy2arclen(x,y,xnot) % the arclength to each point on the curve with x coordinate xnot is % returned.  In this form, xnot must be a single scalar value and the length % of a will be greater than 1 if the curve is multi-valued. The 2 argument % form is the most efficient since no validity checking must be done to % determine if points lie on the curve or not. % % 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   if( nargin == 2) 	n=length(x); 	xx=x(2:n); 	yy=y(2:n); 	d=sqrt( (x(1:n-1)-xx).^2 + (y(1:n-1)-yy).^2 ); 	ind=find(isnan(d)); 	if(length(ind)>0) 		d(ind)=zeros(size(ind)); 	end 	a=zeros(size(x)); 	a(2:n)=cumsum(d); 	return; end if( nargin == 3 ) 	if(length(xnot)>1) 		error('xnot must be a scalar when three arguments are supplied'); 	end 	ynot=ycurve(x,y,xnot); 	if(length(ynot)>1) 		xnot=xnot*ones(size(ynot)); 	end end  n=length(xnot); anodes=xy2arclen(x,y); a=zeros(size(xnot));  for k=1:n  	m=oncurve(x,y,xnot(k),ynot(k)); 	 	if(m==0) 		a(k)=NaN; 	else 	 % note the explicit use of m(1) here. If m has more than one value, then 	 % the curve is multivalued and that will not be handled correctly except int 	 % the case of logsec segments which are linked at the multi valued points 		ainc=sqrt( (x(m(1))-xnot(k)).^2 + (y(m(1))-ynot(k)).^2); 		a(k)=anodes(m(1))+ainc; 	end 	 end