function nnlist = find_nn(xc,yc,m,order)% PURPOSE: finds observations containing m nearest neighbors, fast but high memory version%          to each observation and returns an index to these neighboring observations% --------------------------------------------------------% USAGE: nnindex = find_nn(xc,yc,m)%       where: %             xc = x-coordinate for each obs (nobs x 1)%             yc = y-coordinate for each obs (nobs x 1)%             m  = # of nearest neighbors to be found%          order = 1, 2, 3, or 4. (default = 2)%                  This limits the extent to search for neighbors to the sum of the delaunay orders%                  e.g., delorder=2 limits the search to the delaunay neighbors and the neighbors of neighbors%                  Lower values of delorder speed computation and reduce memory. % --------------------------------------------------------% RETURNS: an (nobs x m) matrix of indices to the m neighbors% --------------------------------------------------------% NOTES: nnindex takes a form such that: ind = nnindex(i,:)';%        y(ind,1)%        would pull out the nn nearest neighbor observations to%        y(i,1), and y(ind,1)/m would represent an avg of these%        This function is a fneighbors2 from R. Kelley Pace's spatial%        statistics toolbox % --------------------------------------------------------% SEE ALSO: find_neighbors, make_nnw which constructs a standardized spatial %           weight matrix based on these Delaunay nearest neighbors% --------------------------------------------------------% written by:% James P. LeSage, Dept of Economics% University of Toledo% 2801 W. Bancroft St,% Toledo, OH 43606% jlesage@spatial-econometrics.com% NOTE: this function draws on ideas from the Spatial Statistics Toolbox%       by R. Kelley Pace (that I stole to construct this function)if nargin == 3order = 2;[W1,W2,W3] = xy2cont(xc,yc);nnlist = fneighbors2(W2,xc,yc,m,order);elseif nargin == 4[W1,W2,W3] = xy2cont(xc,yc);nnlist = fneighbors2(W2,xc,yc,m,order);elseerror('find_nn: Wrong # of input arguments');end;