74 lines
2.0 KiB
Matlab
Executable File
74 lines
2.0 KiB
Matlab
Executable File
function Y=diff(varargin)
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%DIFF (overloaded)
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X = varargin{1};
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n = X.dim(1);
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m = X.dim(2);
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switch nargin
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case 1
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if n == 1
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% Default is diff along first dimension, unless we only have
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% one row. This happens to be the case in which the core function operates
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Y = differ(X);
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else
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% MATLAB stadnard, just diff along first dimension. Reuse core
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% code by transposing matrix
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Y = differ(X')';
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end
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return
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case 2
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% Note that MATLAB diff(randn(2,4),2) will cause a diff in two
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% different directions.
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if n == 1
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if varargin{2}==1 || isempty(varargin{2})
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Y = differ(X);
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else
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% Recursive use
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Y = diff(differ(X),varargin{2}-1);
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end
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else
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if varargin{2}==1 || isempty(varargin{2})
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Y = differ(X')';
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else
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% Recursive use
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Y = diff(differ(X')',varargin{2}-1);
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end
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end
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case 3
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if X.dim(varargin{3})-varargin{2} <=0
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dim = X.dim;
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dim(varargin{3}) = 0;
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Y = zeros(dim);
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elseif varargin{2}==1
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if varargin{3} == 2
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Y = differ(X);
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elseif varargin{3} == 1 || isempty(varargin{3})
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Y = differ(X')';
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end
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elseif varargin{2} > 1
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% Recursive call for higher-order diff
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Y = diff(diff(X,varargin{2}-1,varargin{3}),1,varargin{3});
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return
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end
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otherwise
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error('To many input arguments.')
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end
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function Y = differ(X)
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n = X.dim(1);
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m = X.dim(2);
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Y = X;
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shift = [-speye(m-1) spalloc(m-1,1,0)] + [spalloc(m-1,1,0) speye(m-1)];
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shift = kron(shift,speye(n));
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Y.basis = shift*X.basis;
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Y.dim(1) = n;
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Y.dim(2) = m - 1;
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% Reset info about conic terms
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Y.conicinfo = [0 0];
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Y = flush(Y);
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Y = clean(Y); |