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%DIFF Difference and approximate derivative. % DIFF(X), for a vector X, is [X(2)-X(1) X(3)-X(2) ... X(n)-X(n-1)]. % DIFF(X), for a matrix X, is the matrix of row differences, % [X(2:n,:) - X(1:n-1,:)]. % DIFF(X), for an N-D array X, is the difference along the first % non-singleton dimension of X. % DIFF(X,N) is the N-th order difference along the first non-singleton % dimension (denote it by DIM). If N >= size(X,DIM), DIFF takes % successive differences along the next non-singleton dimension. % DIFF(X,N,DIM) is the Nth difference function along dimension DIM. % If N >= size(X,DIM), DIFF returns an empty array. % % Examples: % h = .001; x = 0:h:pi; % diff(sin(x.^2))/h is an approximation to 2*cos(x.^2).*x % diff((1:10).^2) is 3:2:19 % % If X = [3 7 5 % 0 9 2] % then diff(X,1,1) is [-3 2 -3], diff(X,1,2) is [4 -2 % 9 -7], % diff(X,2,2) is the 2nd order difference along the dimension 2, and % diff(X,3,2) is the empty matrix. % % See also GRADIENT, SUM, PROD. % Copyright 1984-2005 The MathWorks, Inc. % Built-in function.