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maint: Update copyright dates.
author John W. Eaton <jwe@octave.org>
date Wed, 22 Feb 2017 12:39:29 -0500
parents e9a0469dedd9
children 092078913d54
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1 ## Copyright (C) 2016-2017 Markus Muetzel
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2 ##
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3 ## This file is part of Octave.
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4 ##
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5 ## Octave is free software; you can redistribute it and/or modify it
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6 ## under the terms of the GNU General Public License as published by
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7 ## the Free Software Foundation; either version 3 of the License, or (at
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8 ## your option) any later version.
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9 ##
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10 ## Octave is distributed in the hope that it will be useful, but
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11 ## WITHOUT ANY WARRANTY; without even the implied warranty of
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12 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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13 ## General Public License for more details.
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14 ##
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15 ## You should have received a copy of the GNU General Public License
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16 ## along with Octave; see the file COPYING. If not, see
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17 ## <http://www.gnu.org/licenses/>.
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18
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19 ## Undocumented internal function.
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20
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21 ## -*- texinfo -*-
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22 ## @deftypefn {} {@var{isoval} =} __calc_isovalue_from_data__ (@var{data})
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23 ## Calculate a @nospell{"good"} iso value from histogram of data.
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24 ## @end deftypefn
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25
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26 ## called from isocaps, isosurface
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27
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28 function isoval = __calc_isovalue_from_data__ (data)
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29
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30 ## use a maximum of 10,000-20,000 samples to limit runtime of hist
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31 step = 1;
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32 ndata = numel (data);
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33 if (ndata > 20_000)
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34 step = floor (ndata / 10_000);
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35 data = data(1:step:end);
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36 ndata = numel (data);
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37 endif
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38
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39 num_bins = 100;
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40 [bin_count, bin_centers] = hist (data(:), num_bins);
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41
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42 ## if one of the first two bins contains more than 10 times the count as
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43 ## compared to equally distributed data, remove both (zero-padded + noise)
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44 if (any (bin_count(1:2) > 10 * (ndata / num_bins)))
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45 bin_count(1:2) = [];
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46 bin_centers(1:2) = [];
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47 endif
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48
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49 ## if bins have low counts, remove them (but keep them if we would lose
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50 ## more than 90% of bins)
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51 bins_to_remove = find (bin_count < max (bin_count)/50);
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52 if (length (bins_to_remove) < .9 * num_bins)
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53 bin_centers(bins_to_remove) = [];
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54 endif
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55
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56 ## select middle bar of histogram with previous conditions
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57 isoval = bin_centers(floor (numel (bin_centers) / 2));
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58
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59 endfunction