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1 # Copyright (C) 1994 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 the |
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7 # Free Software Foundation; either version 2, or (at your option) any |
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8 # later version. |
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9 # |
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10 # Octave is distributed in the hope that it will be useful, but WITHOUT |
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11 # ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
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12 # FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
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13 # 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, 675 Mass Ave, Cambridge, MA 02139, USA. |
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18 |
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19 function [nn, xx] = hist (y, x) |
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20 |
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21 # usage: [NN, XX] = hist (Y, X) or hist (Y, X) |
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22 # |
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23 # Produce histogram counts or plots. |
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24 # |
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25 # With one vector input argument, plot a histogram of the values with |
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26 # 10 bins. The range of the histogram bins is determined by the range |
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27 # of the data. |
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28 # |
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29 # Given a second scalar argument, use that as the number of bins. |
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30 # |
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31 # Given a second vector argument, use that as the centers of the bins, |
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32 # with the width of the bins determened from the adjacent values in |
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33 # the vector. |
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34 # |
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35 # Extreme values are lumped in the first and last bins. |
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36 # |
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37 # With two output arguments, produce the values NN and XX such that |
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38 # bar (XX, NN) will plot the histogram. |
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39 # |
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40 # See also: bar |
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41 |
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42 if (nargin < 1 || nargin > 2) |
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43 error ("usage: [nn, xx] = hist (y, x)"); |
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44 endif |
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45 |
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46 if (is_vector (y)) |
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47 max_val = max (y); |
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48 min_val = min (y); |
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49 else |
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50 error ("hist: first argument must be a vector"); |
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51 endif |
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52 |
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53 if (nargin == 1) |
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54 n = 10; |
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55 delta = (max_val - min_val) / n / 2; |
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56 x = linspace (min_val+delta, max_val-delta, n); |
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57 cutoff = x + delta; |
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58 elseif (nargin == 2) |
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59 if (is_scalar (x)) |
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60 n = x; |
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61 if (n <= 0) |
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62 error ("hist: number of bins must be positive"); |
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63 endif |
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64 delta = (max_val - min_val) / n / 2; |
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65 x = linspace (min_val+delta, max_val-delta, n); |
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66 cutoff = x + delta; |
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67 elseif (is_vector (x)) |
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68 tmp = sort (x); |
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69 if (any (tmp != x)) |
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70 fprintf (stderr, "warning: hist: bin values not sorted on input\n"); |
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71 x = tmp; |
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72 endif |
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73 n = length (x); |
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74 cutoff = zeros (1, n-1); |
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75 for i = 1:n-1 |
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76 cutoff (i) = (x (i) + x (i+1)) / 2; |
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77 endfor |
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78 else |
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79 error ("hist: second argument must be a scalar or a vector"); |
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80 endif |
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81 endif |
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82 |
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83 freq = zeros (1, n); |
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84 freq (1) = sum (y < cutoff (1)); |
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85 for i = 2:n-1 |
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86 freq (i) = sum (y >= cutoff (i-1) & y < cutoff (i)); |
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87 endfor |
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88 freq (n) = sum (y >= cutoff (n-1)); |
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89 |
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90 # With Octave 1.0, nargout is never zero, so we have to do this: |
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91 |
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92 nn = freq; |
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93 xx = x; |
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94 if (nargout != 2) |
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95 bar (xx, nn); |
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96 endif |
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97 |
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98 # Once 1.1 is released, we can do this instead: |
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99 # |
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100 # if (nargout == 2) |
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101 # nn = freq; |
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102 # xx = x; |
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103 # else |
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104 # bar (x, freq); |
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105 # endif |
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106 |
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107 endfunction |
