/usr/share/octave/site/m/vlfeat/toolbox/misc/vl_colsubset.m is in octave-vlfeat 0.9.17+dfsg0-6+b1.
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 | function [Y, sel] = vl_colsubset(X,n,varargin)
% VL_COLSUBSET Select a given number of columns
% Y = VL_COLSUBSET(X, N) returns a random subset Y of N columns of
% X. The selection is order-preserving and without replacement. If N
% is larger or equal to the number of columns of X (e.g. N = Inf),
% then the function returns all the columns (i.e., Y = X).
%
% If 0 < N < 1, then the function returns a fraction N of the
% columns (rounded to the closest integer).
%
% [Y, SEL] = VL_COLSUBSET(...) returns the indexes SEL of the
% selected columns.
%
% The function accepts the following options:
%
% Beginning::
% Returns the fist N columns.
%
% Ending::
% Returns the last N columns.
%
% Random:: [default]
% Returns N columns selected at random (using RANDPERM()).
%
% Uniform::
% Returns N uniformly spaced columns.
%
% Largest::
% Returns the N largest columns (using SORTROWS()).
%
% Smallest::
% Returns the N smallest columns (using SORTROWS()).
%
% See also: VL_HELP().
% Authors: Andrea Vedaldi
% Copyright (C) 2007-12 Andrea Vedaldi and Brian Fulkerson.
% All rights reserved.
%
% This file is part of the VLFeat library and is made available under
% the terms of the BSD license (see the COPYING file).
if nargin < 2, n = 1 ; end
mode = 'random' ;
i = 1 ;
while i <= length(varargin)
switch lower(varargin{i})
case {'beginning', ...
'ending', ...
'random', ...
'uniform', ...
'largest', ...
'smallest'}
mode = lower(varargin{1}) ;
i = i + 1 ;
otherwise
error('Unknown option ''%s''.', varargin{i}) ;
end
end
m = size(X,2) ;
if n < 0, error('N must not be smaller than 0.') ; end
if n ~= round(n)
if n > 1
error('N must be a natural number, +inf, or a fraction in 0 and 1.') ;
end
n = round(m * n) ;
end
n = min(m,n) ;
switch mode
case 'random'
perm = randperm(m) ;
sel = sort(perm(1:n)) ;
case 'beginning'
perm = 1:m ;
sel = sort(perm(1:n)) ;
case 'ending'
perm = m:-1:1 ;
sel = sort(perm(1:n)) ;
case 'uniform'
if n < 1
sel = [] ;
else
sel = round(linspace(1, m, min(m,n))) ;
end
case 'largest'
[drop, perm] = sortrows(X') ;
sel = sort(perm(end-n+1:end)) ;
case 'smallest'
[drop, perm] = sortrows(X') ;
sel = sort(perm(1:n)) ;
end
Y = X(:, sel) ;
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