/usr/share/freemat/toolbox/general/diff.m is in freemat-data 4.0-5.
This file is owned by root:root, with mode 0o644.
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 | % DIFF DIFF Difference Function
%
% Usage
%
%
% y=diff(x)
% y=diff(x,k)
% y=diff(x,k,dim)
%
% Produce difference of successive vector elements.
%
% If x is a vector of length n, diff (x) is the
% vector of first differences
% \[
% [x_2 - x_1, ..., x_n - x_{n-1}].
% \]
%
% If x is a matrix, diff (x) is the matrix of column
% differences along the first non-singleton dimension.
%
% The second argument is optional. If supplied, diff (x,k),
% where k is a nonnegative integer, returns the
% k-th differences. It is possible that k is larger than
% then first non-singleton dimension of the matrix. In this case,
% diff continues to take the differences along the next
% non-singleton dimension.
%
% The dimension along which to take the difference can be explicitly
% stated with the optional variable dim. In this case the
% k-th order differences are calculated along this dimension.
% In the case where k exceeds size (x, dim)
% then an empty matrix is returned.
%
% Copyright (C) 1995, 1996, 1999, 2000, 2002, 2004, 2005, 2006, 2007
% Kurt Hornik
%%
%% Copyright (C) 2008 Samit Basu, Eugene Ingerman
%%
%% This file is adopted in FreeMat from Octave under the conditions of the GNU
%% General Public License
%
%
% Octave is free software; you can redistribute it and/or modify it
% under the terms of the GNU General Public License as published by
% the Free Software Foundation; either version 3 of the License, or (at
% your option) any later version.
%
% Octave is distributed in the hope that it will be useful, but
% WITHOUT ANY WARRANTY; without even the implied warranty of
% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
% General Public License for more details.
%
% You should have received a copy of the GNU General Public License
% along with Octave; see the file COPYING. If not, see
% <http://www.gnu.org/licenses/>.
% Author: KH <Kurt.Hornik@wu-wien.ac.at>
% Created: 2 February 1995
% Adapted-By: jwe
function x = diff (x, k, dim)
if (nargin < 1 || nargin > 3)
error('incorrect number of parameters');
end
if (nargin < 2 || isempty(k))
k = 1;
else
if ( ~ (isscalar (k) && k == round (k) && k >= 0))
error ('diff: k must be a nonnegative integer');
elseif (k == 0)
return;
end
end
nd = ndims (x);
sz = size (x);
if (nargin ~= 3)
%% Find the first non-singleton dimension
dim = 1;
while (dim < nd + 1 && sz (dim) == 1)
dim = dim + 1;
end
if (dim > nd)
dim = 1;
end
else
if (~ (isscalar (dim) && dim == round (dim)) && dim > 0 && dim < (nd + 1))
error ('diff: dim must be an integer and valid dimension');
end
end
% if (ischar (x))
% error ('diff: symbolic differentiation not (yet) supported');
% end
if (nargin == 3)
if (sz (dim) <= k)
sz(dim) = 0;
if (isa(x,'single'))
x = zeros (sz,'single');
else
x = zeros(sz);
end
else
n = sz (dim);
idx1 = cell ();
for i = 1:nd
idx1{i} = 1:sz(i);
end
idx2 = idx1;
for i = 1 : k;
idx1{dim} = 2 : (n - i + 1);
idx2{dim} = 1 : (n - i);
x = x(idx1{:}) - x(idx2{:});
end
end
else
if (sum (sz - 1) < k)
if (isa(x,'single'))
x = single([]);
else
x = [];
end;
else
idx1 = cell ();
for i = 1:nd
idx1{i} = 1:sz(i);
end
idx2 = idx1;
while (k)
n = sz (dim);
for i = 1 : min (k, n - 1)
idx1{dim} = 2 : (n - i + 1);
idx2{dim} = 1 : (n - i);
x = x(idx1{:}) - x(idx2{:});
end
idx1{dim} = 1;
idx2{dim} = 1;
k = k - min (k, n - 1);
dim = dim + 1;
end
end
end
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