54 lines
1.9 KiB
Mathematica
54 lines
1.9 KiB
Mathematica
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function B = expand(A, S)
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%EXPAND Replicate and tile each element of an array, similar to repmat.
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% EXPAND(A,SZ), for array A and vector SZ replicates each element of A by
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% SZ. The results are tiled into an array in the same order as the
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% elements of A, so that the result is size: size(A).*SZ. Therefore the
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% number of elements of SZ must equal the number of dimensions of A, or in
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% MATLAB syntax: length(size(A))==length(SZ) must be true.
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% The result will have the same number of dimensions as does A.
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% There is no restriction on the number of dimensions for input A.
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%
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% Examples:
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%
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% A = [1 2; 3 4]; % 2x2
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% SZ = [6 5];
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% B = expand(A,[6 5]) % Creates a 12x10 array.
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%
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% The following demonstrates equivalence of EXPAND and expansion acheived
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% through indexing the individual elements of the array:
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%
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% A = 1; B = 2; C = 3; D = 4; % Elements of the array to be expanded.
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% Mat = [A B;C D]; % The array to expand.
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% SZ = [2 3]; % The expansion vector.
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% ONES = ones(SZ); % The index array.
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% ExpMat1 = [A(ONES),B(ONES);C(ONES),D(ONES)]; % Element expansion.
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% ExpMat2 = expand(Mat,SZ); % Calling EXPAND.
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% isequal(ExpMat1,ExpMat2) % Yes
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%
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%
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% See also, repmat, meshgrid, ones, zeros, kron
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%
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% Author: Matt Fig
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% Date: 6/20/2009
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% Contact: popkenai@yahoo.com
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if nargin < 2
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error('Size vector must be provided. See help.');
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end
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SA = size(A); % Get the size (and number of dimensions) of input.
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if length(SA) ~= length(S)
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error('Length of size vector must equal ndims(A). See help.')
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elseif any(S ~= floor(S))
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error('The size vector must contain integers only. See help.')
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end
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T = cell(length(SA), 1);
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for ii = length(SA) : -1 : 1
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H = zeros(SA(ii) * S(ii), 1); % One index vector into A for each dim.
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H(1 : S(ii) : SA(ii) * S(ii)) = 1; % Put ones in correct places.
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T{ii} = cumsum(H); % Cumsumming creates the correct order.
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end
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B = A(T{:}); % Feed the indices into A.
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