function d = cosine(a,b,df)% EUCLIDEAN - computes Euclidean distance matrix%% E = euclidean(A,B)%%    A - (DxM) matrix %    B - (DxN) matrix%    df = 1, force diagonals to be zero; 0 (default), do not force% % Returns:%    E - (MxN) Cosine distances between vectors in A and B%%% Description : %    This fully vectorized (VERY FAST!) m-file computes the %    Euclidean distance between two vectors by:%%                 ||A-B|| = (1 - A.B/|| A |||| B||)%% Example : %    A = rand(400,100); B = rand(400,200);%    d = distance(A,B);%% Author: vikas Sindhwani% June 2004if (nargin < 2)   error('Not enough input arguments');endif (nargin < 3)   df = 0;    % by default, do not force 0 on the diagonalendif (size(a,1) ~= size(b,1))   error('A and B should be of same dimensionality');endif ~(isreal(a)*isreal(b))   disp('Warning: running distance.m with imaginary numbers.  Results may be off.'); endif (size(a,1) == 1)  a = [a; zeros(1,size(a,2))];   b = [b; zeros(1,size(b,2))]; endaa=sum(a.*a); bb=sum(b.*b); ab=a'*b; %d = sqrt(repmat(aa',[1 size(bb,2)]) + repmat(bb,[size(aa,2) 1]) - 2*ab);d=ones(size(a,2),size(b,2))-(1./sqrt(kron(aa',bb))).*ab;% make sure result is all reald = real(d); % force 0 on the diagonal? if (df==1)  d = d.*(1-eye(size(d)));end