www.pudn.com > geometric.rar > surround.m, change:2004-08-13,size:2724b

function ind=surround(x,xtest) % ind=surround(x,xtest) % % SURROUND returns a vector of indicies indicating how the vector % x surrounds xtest which must be a scalar. If % isempty(ind) then xtest lies outside the range of x. Otherwise, % ind will be the index of a point in x just greater (or less) than % xtest. Thus the following will be true: % x(ind) <= xtest < x(ind+1) % or % x(ind) >= xtest > x(ind+1) % % So, for if xtest is an interior point for the vector x, % ind and ind+1 select those points in x which surround (or bracket) % xtest. Note that x need not be monotonic. If the xtest is surrounded % more than once by x, then ind will be a vector. % example: x=1:10; % >>surround(x,-1) % returns [] % >>surround(x,3) % returns 3 % now let x=[1:10 9:-1:1] % >>surround(x,3) % returns 3 17 % >>surround(x,pi) % returns 3 16 % % G.F. Margrave % Jan 1994, revised Jan 95 % % 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 n=length(x); x1=x(1:n-1); x2=x(2:n); ind=find( (x1<=xtest & x2>xtest ) | ... (x1>=xtest & x2 < xtest ) );