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1 ### Copyright (C) 1996 John W. Eaton |
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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 2, or (at your option) |
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8 ### 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, write to the Free |
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17 ### Software Foundation, 59 Temple Place - Suite 330, Boston, MA |
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18 ### 02111-1307, USA. |
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19 |
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20 ## usage: [NN, XX] = hist (Y, X) or hist (Y, X) |
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21 ## |
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22 ## Produce histogram counts or plots. |
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23 ## |
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24 ## With one vector input argument, plot a histogram of the values with |
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25 ## 10 bins. The range of the histogram bins is determined by the range |
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26 ## of the data. |
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27 ## |
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28 ## Given a second scalar argument, use that as the number of bins. |
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29 ## |
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30 ## Given a second vector argument, use that as the centers of the bins, |
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31 ## with the width of the bins determened from the adjacent values in |
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32 ## the vector. |
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33 ## |
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34 ## Extreme values are lumped in the first and last bins. |
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35 ## |
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36 ## With two output arguments, produce the values NN and XX such that |
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37 ## bar (XX, NN) will plot the histogram. |
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38 ## |
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39 ## See also: bar |
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40 |
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41 function [nn, xx] = hist (y, x) |
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42 |
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43 if (nargin < 1 || nargin > 2) |
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44 usage ("[nn, xx] = hist (y, x)"); |
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45 endif |
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46 |
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47 if (is_vector (y)) |
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48 max_val = max (y); |
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49 min_val = min (y); |
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50 else |
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51 error ("hist: first argument must be a vector"); |
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52 endif |
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53 |
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54 if (nargin == 1) |
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55 n = 10; |
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56 delta = (max_val - min_val) / n / 2; |
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57 x = linspace (min_val+delta, max_val-delta, n); |
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58 cutoff = x + delta; |
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59 elseif (nargin == 2) |
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60 if (is_scalar (x)) |
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61 n = x; |
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62 if (n <= 0) |
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63 error ("hist: number of bins must be positive"); |
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64 endif |
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65 delta = (max_val - min_val) / n / 2; |
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66 x = linspace (min_val+delta, max_val-delta, n); |
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67 cutoff = x + delta; |
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68 elseif (is_vector (x)) |
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69 tmp = sort (x); |
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70 if (any (tmp != x)) |
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71 warning ("hist: bin values not sorted on input"); |
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72 x = tmp; |
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73 endif |
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74 n = length (x); |
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75 cutoff = zeros (1, n-1); |
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76 for i = 1:n-1 |
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77 cutoff (i) = (x (i) + x (i+1)) / 2; |
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78 endfor |
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79 else |
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80 error ("hist: second argument must be a scalar or a vector"); |
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81 endif |
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82 endif |
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83 |
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84 freq = zeros (1, n); |
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85 freq (1) = sum (y < cutoff (1)); |
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86 for i = 2:n-1 |
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87 freq (i) = sum (y >= cutoff (i-1) & y < cutoff (i)); |
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88 endfor |
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89 freq (n) = sum (y >= cutoff (n-1)); |
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90 |
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91 if (nargout == 2) |
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92 nn = freq; |
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93 xx = x; |
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94 else |
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95 bar (x, freq); |
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96 endif |
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97 |
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98 endfunction |
