Mercurial > hg > octave-lyh
annotate scripts/general/cumtrapz.m @ 14611:f2ed09ae8d3f
doc: Produce .texi from .txi files using Perl rather than C++.
* munge-texi.pl: New Perl file to generate .texi files from .txi files.
* munge-texi.cc: Remove C++ file for generating .texi files.
* Makefile.am: Change build system to use munge-texi.pl
author | Rik <octave@nomad.inbox5.com> |
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date | Tue, 08 May 2012 21:03:42 -0700 |
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1 ## Copyright (C) 2000-2012 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} =} cumtrapz (@var{y}) |
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21 ## @deftypefnx {Function File} {@var{q} =} cumtrapz (@var{x}, @var{y}) |
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22 ## @deftypefnx {Function File} {@var{q} =} cumtrapz (@dots{}, @var{dim}) |
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23 ## |
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24 ## Cumulative numerical integration of points @var{y} using the trapezoidal |
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25 ## method. |
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26 ## @w{@code{cumtrapz (@var{y})}} computes the cumulative integral of @var{y} |
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27 ## along the first non-singleton dimension. Where @code{trapz} reports |
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28 ## only the overall integral sum, @code{cumtrapz} reports the current partial |
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29 ## sum value at each point of @var{y}. When the argument @var{x} is omitted |
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30 ## an equally spaced @var{x} vector with unit spacing (1) is assumed. |
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31 ## @code{cumtrapz (@var{x}, @var{y})} evaluates the integral with respect to |
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32 ## the spacing in @var{x} and the values in @var{y}. This is useful if the |
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33 ## points in @var{y} have been sampled unevenly. If the optional @var{dim} |
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34 ## argument is given, operate along this dimension. |
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35 ## |
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36 ## If @var{x} is not specified then unit spacing will be used. To scale |
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37 ## the integral to the correct value you must multiply by the actual spacing |
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38 ## value (deltaX). |
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39 ## @seealso{trapz, cumsum} |
5820 | 40 ## @end deftypefn |
41 | |
10549 | 42 ## Author: Kai Habel <kai.habel@gmx.de> |
5820 | 43 ## |
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44 ## also: June 2000 Paul Kienzle (fixes,suggestions) |
5820 | 45 ## 2006-05-12 David Bateman - Modified for NDArrays |
46 | |
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47 function z = cumtrapz (x, y, dim) |
5820 | 48 |
49 if (nargin < 1) || (nargin > 3) | |
6046 | 50 print_usage (); |
5820 | 51 endif |
52 | |
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53 have_xy = have_dim = false; |
5820 | 54 |
55 if (nargin == 3) | |
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56 have_xy = true; |
5820 | 57 have_dim = true; |
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58 elseif (nargin == 2) |
6157 | 59 if (! size_equal (x, y) && isscalar (y)) |
5820 | 60 dim = y; |
61 have_dim = true; | |
62 else | |
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63 have_xy = true; |
5820 | 64 endif |
65 endif | |
66 | |
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67 if (have_xy) |
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68 nd = ndims (y); |
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69 sz = size (y); |
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70 else |
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71 nd = ndims (x); |
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72 sz = size (x); |
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73 endif |
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74 |
5820 | 75 if (! have_dim) |
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76 ## Find the first non-singleton dimension. |
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77 (dim = find (sz > 1, 1)) || (dim = 1); |
5820 | 78 else |
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79 if (!(isscalar (dim) && dim == fix (dim)) |
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80 || !(1 <= dim && dim <= nd)) |
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81 error ("trapz: DIM must be an integer and a valid dimension"); |
5820 | 82 endif |
83 endif | |
84 | |
85 n = sz(dim); | |
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86 idx1 = idx2 = repmat ({':'}, [nd, 1]); |
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87 idx1{dim} = 2 : n; |
5820 | 88 idx2{dim} = 1 : (n - 1); |
89 | |
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90 if (! have_xy) |
5820 | 91 z = 0.5 * cumsum (x(idx1{:}) + x(idx2{:}), dim); |
92 else | |
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93 if (isvector (x) && !isvector (y)) |
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94 if (length (x) != sz(dim)) |
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95 error ("cumtrapz: length of X and length of Y along DIM must match"); |
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96 endif |
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97 ## Reshape vector to point along dimension DIM |
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98 shape = ones (nd, 1); |
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99 shape(dim) = sz(dim); |
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100 x = reshape (x, shape); |
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101 z = 0.5 * cumsum (bsxfun (@times, diff (x), y(idx1{:}) + y(idx2{:})), dim); |
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102 else |
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103 if (! size_equal (x, y)) |
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104 error ("cumtrapz: X and Y must have same shape"); |
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105 endif |
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106 z = 0.5 * cumsum (diff (x, 1, dim) .* (y(idx1{:}) + y(idx2{:})), dim); |
5820 | 107 endif |
108 endif | |
109 | |
110 sz(dim) = 1; | |
111 z = cat (dim, zeros (sz), z); | |
112 | |
113 endfunction | |
114 | |
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115 |
5820 | 116 %!shared x1,x2,y |
117 %! x1 = [0,0,0;2,2,2]; | |
118 %! x2 = [0,2,4;0,2,4]; | |
119 %! y = [1,2,3;4,5,6]; | |
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120 %!assert (cumtrapz (y), [0,0,0;2.5,3.5,4.5]) |
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121 %!assert (cumtrapz (x1,y), [0,0,0;5,7,9]) |
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122 %!assert (cumtrapz (y,1), [0,0,0;2.5,3.5,4.5]) |
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123 %!assert (cumtrapz (x1,y,1), [0,0,0;5,7,9]) |
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124 %!assert (cumtrapz (y,2), [0,1.5,4;0,4.5,10]) |
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125 %!assert (cumtrapz (x2,y,2), [0,3,8;0,9,20]) |
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126 %% Test ND-array implementation |
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127 %!shared x1,x2,y |
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128 %! x1 = 1:3; |
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129 %! x2 = reshape ([0,2,4;0,2,4], [1 2 3]); |
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130 %! y = reshape ([1,2,3;4,5,6], [1 2 3]); |
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131 %!assert (cumtrapz (y,3), reshape ([0,1.5,4;0,4.5,10],[1 2 3])) |
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132 %!assert (cumtrapz (x1,y,3), reshape ([0,1.5,4;0,4.5,10],[1 2 3])) |
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133 %!assert (cumtrapz (x2,y,3), reshape ([0,3,8;0,9,20],[1 2 3])) |
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134 |