Mercurial > octave-nkf
annotate scripts/general/trapz.m @ 20652:a3b9ee5c040a
Replace bsxfun with broadcasting for performance with complex inputs (bug #38628).
cumtrapz.m, quadgk.m, trapz.m, center.m, zscore.m: Replace bsxfun with
broadcasting for performance where inputs might be complex.
author | Rik <rik@octave.org> |
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date | Mon, 12 Oct 2015 21:28:32 -0700 |
parents | 7503499a252b |
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1 ## Copyright (C) 2000-2015 Kai Habel |
5820 | 2 ## |
3 ## This file is part of Octave. | |
4 ## | |
5 ## Octave is free software; you can redistribute it and/or modify it | |
6 ## under the terms of the GNU General Public License as published by | |
7016 | 7 ## the Free Software Foundation; either version 3 of the License, or (at |
8 ## your option) any later version. | |
5820 | 9 ## |
10 ## Octave is distributed in the hope that it will be useful, but | |
11 ## WITHOUT ANY WARRANTY; without even the implied warranty of | |
12 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
13 ## General Public License for more details. | |
14 ## | |
15 ## You should have received a copy of the GNU General Public License | |
7016 | 16 ## along with Octave; see the file COPYING. If not, see |
17 ## <http://www.gnu.org/licenses/>. | |
5820 | 18 |
19 ## -*- texinfo -*- | |
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20 ## @deftypefn {Function File} {@var{q} =} trapz (@var{y}) |
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21 ## @deftypefnx {Function File} {@var{q} =} trapz (@var{x}, @var{y}) |
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22 ## @deftypefnx {Function File} {@var{q} =} trapz (@dots{}, @var{dim}) |
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23 ## |
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24 ## Numerically evaluate the integral of points @var{y} using the trapezoidal |
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25 ## method. |
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26 ## |
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27 ## @w{@code{trapz (@var{y})}} computes the integral of @var{y} along the first |
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28 ## non-singleton dimension. When the argument @var{x} is omitted an equally |
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29 ## spaced @var{x} vector with unit spacing (1) is assumed. |
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30 ## @code{trapz (@var{x}, @var{y})} evaluates the integral with respect to the |
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31 ## spacing in @var{x} and the values in @var{y}. This is useful if the points |
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32 ## in @var{y} have been sampled unevenly. |
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33 ## |
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34 ## If the optional @var{dim} argument is given, operate along this dimension. |
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35 ## |
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36 ## Application Note: If @var{x} is not specified then unit spacing will be |
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37 ## used. To scale the integral to the correct value you must multiply by the |
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38 ## actual spacing value (deltaX). As an example, the integral of @math{x^3} |
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39 ## over the range [0, 1] is @math{x^4/4} or 0.25. The following code uses |
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40 ## @code{trapz} to calculate the integral in three different ways. |
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41 ## |
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42 ## @example |
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43 ## @group |
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44 ## x = 0:0.1:1; |
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45 ## y = x.^3; |
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46 ## q = trapz (y) |
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47 ## @result{} q = 2.525 # No scaling |
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48 ## q * 0.1 |
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49 ## @result{} q = 0.2525 # Approximation to integral by scaling |
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50 ## trapz (x, y) |
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51 ## @result{} q = 0.2525 # Same result by specifying @var{x} |
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52 ## @end group |
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53 ## @end example |
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54 ## |
5820 | 55 ## @seealso{cumtrapz} |
56 ## @end deftypefn | |
57 | |
10549 | 58 ## Author: Kai Habel <kai.habel@gmx.de> |
5820 | 59 ## |
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60 ## also: June 2000 - Paul Kienzle (fixes,suggestions) |
5820 | 61 ## 2006-05-12 David Bateman - Modified for NDArrays |
62 | |
63 function z = trapz (x, y, dim) | |
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64 |
5820 | 65 if (nargin < 1) || (nargin > 3) |
6046 | 66 print_usage (); |
5820 | 67 endif |
68 | |
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69 have_xy = have_dim = false; |
5820 | 70 |
71 if (nargin == 3) | |
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72 have_xy = true; |
5820 | 73 have_dim = true; |
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74 elseif (nargin == 2) |
6157 | 75 if (! size_equal (x, y) && isscalar (y)) |
5820 | 76 dim = y; |
77 have_dim = true; | |
78 else | |
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79 have_xy = true; |
5820 | 80 endif |
81 endif | |
82 | |
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83 if (have_xy) |
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84 nd = ndims (y); |
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85 sz = size (y); |
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86 else |
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87 nd = ndims (x); |
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88 sz = size (x); |
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89 endif |
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90 |
5820 | 91 if (! have_dim) |
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92 ## Find the first non-singleton dimension. |
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93 (dim = find (sz > 1, 1)) || (dim = 1); |
5820 | 94 else |
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95 if (!(isscalar (dim) && dim == fix (dim)) |
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96 || !(1 <= dim && dim <= nd)) |
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97 error ("trapz: DIM must be an integer and a valid dimension"); |
5820 | 98 endif |
99 endif | |
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100 |
5820 | 101 n = sz(dim); |
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102 idx1 = idx2 = repmat ({':'}, [nd, 1]); |
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103 idx1{dim} = 2 : n; |
5820 | 104 idx2{dim} = 1 : (n - 1); |
105 | |
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106 if (! have_xy) |
5820 | 107 z = 0.5 * sum (x(idx1{:}) + x(idx2{:}), dim); |
108 else | |
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109 if (isvector (x) && ! isvector (y)) |
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110 if (length (x) != sz(dim)) |
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111 error ("trapz: length of X and length of Y along DIM must match"); |
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112 endif |
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113 ## Reshape vector to point along dimension DIM |
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114 shape = ones (nd, 1); |
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115 shape(dim) = sz(dim); |
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116 x = reshape (x, shape); |
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117 z = 0.5 * sum (diff (x) .* (y(idx1{:}) + y(idx2{:})), dim); |
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118 else |
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119 if (! size_equal (x, y)) |
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120 error ("trapz: X and Y must have same shape"); |
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121 endif |
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122 z = 0.5 * sum (diff (x, 1, dim) .* (y(idx1{:}) + y(idx2{:})), dim); |
5820 | 123 endif |
124 endif | |
125 endfunction | |
126 | |
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127 |
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128 %!assert (trapz (1:5), 12) |
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129 %!assert (trapz (0:0.5:2,1:5), 6) |
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130 %!assert (trapz ([1:5;1:5].',1), [12,12]) |
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131 %!assert (trapz ([1:5;1:5],2), [12;12]) |
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132 %!assert (trapz (repmat (reshape (1:5,1,1,5),2,2), 3), [12 12; 12 12]) |
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133 %!assert (trapz ([0:0.5:2;0:0.5:2].',[1:5;1:5].',1), [6, 6]) |
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134 %!assert (trapz ([0:0.5:2;0:0.5:2],[1:5;1:5],2), [6; 6]) |
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135 %!assert (trapz (repmat (reshape ([0:0.5:2],1,1,5),2,2), ... |
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136 %! repmat (reshape (1:5,1,1,5),2,2), 3), [6 6; 6 6]) |
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137 %!assert (trapz (0:0.5:2,[(1:5)',(1:5)']), [6, 6]) |
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138 %!assert (trapz (0:0.5:2,[(1:5);(1:5)],2), [6; 6]) |
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139 %!assert (trapz (0:0.5:2,repmat (reshape (1:5,1,1,5),2,2),3), [6 6; 6 6]) |
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140 |