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annotate scripts/polynomial/splinefit.m @ 21546:f7f97d7e9294
doc: Wrap m-file docstrings to 79 characters + newline (80 total).
* isrecording.m, soundsc.m, delaunay3.m, cell2mat.m, cumtrapz.m, del2.m,
inputParser.m, interp1.m, interp3.m, narginchk.m, profile.m,
validateattributes.m, delaunayn.m, tsearchn.m, voronoin.m, brighten.m,
cmunique.m, colorcube.m, imfinfo.m, imshow.m, edit.m, orderfields.m, run.m,
warning_ids.m, ode23.m, ode45.m, odeget.m, integrate_adaptive.m, kahan.m,
ode_struct_value_check.m, runge_kutta_23.m, fminunc.m, fsolve.m, fzero.m,
pkg.m, build.m, specular.m, view.m, bar.m, barh.m, contour3.m, isosurface.m,
line.m, pie.m, pie3.m, quiver3.m, scatter.m, scatter3.m, stem3.m, stemleaf.m,
surfl.m, tetramesh.m, isfigure.m, mkpp.m, pchip.m, residue.m, splinefit.m,
rmpref.m, unique.m, eigs.m, ilu.m, factor.m, factorial.m, gallery.m, hankel.m,
histc.m, ols.m, finv.m, fpdf.m, kruskal_wallis_test.m, weekday.m:
Wrap m-file docstrings to 79 characters + newline (80 total).
author | Rik <rik@octave.org> |
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date | Sun, 27 Mar 2016 15:50:01 -0700 |
parents | 516bb87ea72e |
children | ecce63c99c3f |
rev | line source |
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1 ## Copyright (C) 2012-2015 Ben Abbott, Jonas Lundgren |
14509 | 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 | |
7 ## the Free Software Foundation; either version 3 of the License, or (at | |
8 ## your option) any later version. | |
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 | |
16 ## along with Octave; see the file COPYING. If not, see | |
17 ## <http://www.gnu.org/licenses/>. | |
18 | |
19 ## -*- texinfo -*- | |
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20 ## @deftypefn {} {@var{pp} =} splinefit (@var{x}, @var{y}, @var{breaks}) |
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21 ## @deftypefnx {} {@var{pp} =} splinefit (@var{x}, @var{y}, @var{p}) |
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22 ## @deftypefnx {} {@var{pp} =} splinefit (@dots{}, "periodic", @var{periodic}) |
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23 ## @deftypefnx {} {@var{pp} =} splinefit (@dots{}, "robust", @var{robust}) |
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24 ## @deftypefnx {} {@var{pp} =} splinefit (@dots{}, "beta", @var{beta}) |
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25 ## @deftypefnx {} {@var{pp} =} splinefit (@dots{}, "order", @var{order}) |
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26 ## @deftypefnx {} {@var{pp} =} splinefit (@dots{}, "constraints", @var{constraints}) |
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27 ## |
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28 ## Fit a piecewise cubic spline with breaks (knots) @var{breaks} to the |
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29 ## noisy data, @var{x} and @var{y}. |
14509 | 30 ## |
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31 ## @var{x} is a vector, and @var{y} is a vector or N-D array. If @var{y} is an |
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32 ## N-D array, then @var{x}(j) is matched to @var{y}(:,@dots{},:,j). |
14509 | 33 ## |
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34 ## @var{p} is a positive integer defining the number of intervals along |
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35 ## @var{x}, and @var{p}+1 is the number of breaks. The number of points in |
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36 ## each interval differ by no more than 1. |
14509 | 37 ## |
38 ## The optional property @var{periodic} is a logical value which specifies | |
39 ## whether a periodic boundary condition is applied to the spline. The | |
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40 ## length of the period is @code{max (@var{breaks}) - min (@var{breaks})}. |
14509 | 41 ## The default value is @code{false}. |
42 ## | |
43 ## The optional property @var{robust} is a logical value which specifies | |
44 ## if robust fitting is to be applied to reduce the influence of outlying | |
45 ## data points. Three iterations of weighted least squares are performed. | |
46 ## Weights are computed from previous residuals. The sensitivity of outlier | |
47 ## identification is controlled by the property @var{beta}. The value of | |
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48 ## @var{beta} is restricted to the range, 0 < @var{beta} < 1. The default |
14509 | 49 ## value is @var{beta} = 1/2. Values close to 0 give all data equal |
50 ## weighting. Increasing values of @var{beta} reduce the influence of | |
51 ## outlying data. Values close to unity may cause instability or rank | |
52 ## deficiency. | |
53 ## | |
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54 ## The fitted spline is returned as a piecewise polynomial, @var{pp}, and |
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55 ## may be evaluated using @code{ppval}. |
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56 ## |
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57 ## The splines are constructed of polynomials with degree @var{order}. |
14509 | 58 ## The default is a cubic, @var{order}=3. A spline with P pieces has |
59 ## P+@var{order} degrees of freedom. With periodic boundary conditions | |
60 ## the degrees of freedom are reduced to P. | |
61 ## | |
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62 ## The optional property, @var{constaints}, is a structure specifying linear |
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63 ## constraints on the fit. The structure has three fields, @qcode{"xc"}, |
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64 ## @qcode{"yc"}, and @qcode{"cc"}. |
14509 | 65 ## |
66 ## @table @asis | |
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67 ## @item @qcode{"xc"} |
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68 ## Vector of the x-locations of the constraints. |
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69 ## |
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70 ## @item @qcode{"yc"} |
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71 ## Constraining values at the locations @var{xc}. |
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72 ## The default is an array of zeros. |
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73 ## |
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74 ## @item @qcode{"cc"} |
14509 | 75 ## Coefficients (matrix). The default is an array of ones. The number of |
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76 ## rows is limited to the order of the piecewise polynomials, @var{order}. |
14509 | 77 ## @end table |
78 ## | |
79 ## Constraints are linear combinations of derivatives of order 0 to | |
80 ## @var{order}-1 according to | |
81 ## | |
82 ## @example | |
83 ## @group | |
84 ## @tex | |
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85 ## $cc(1,j) \cdot y(xc(j)) + cc(2,j) \cdot y\prime(xc(j)) + ... = yc(:,\dots,:,j)$. |
14509 | 86 ## @end tex |
87 ## @ifnottex | |
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88 ## cc(1,j) * y(xc(j)) + cc(2,j) * y'(xc(j)) + ... = yc(:,...,:,j). |
14509 | 89 ## @end ifnottex |
90 ## @end group | |
91 ## @end example | |
92 ## | |
93 ## @seealso{interp1, unmkpp, ppval, spline, pchip, ppder, ppint, ppjumps} | |
94 ## @end deftypefn | |
95 | |
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96 function pp = splinefit (x, y, breaks, varargin) |
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97 if (nargin > 3) |
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98 n = cellfun ("isclass", varargin, "char"); |
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99 varargin(n) = lower (varargin(n)); |
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100 try |
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101 props = struct (varargin{:}); |
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102 catch |
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103 print_usage (); |
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104 end_try_catch |
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105 else |
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106 props = struct (); |
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107 endif |
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108 fields = fieldnames (props); |
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109 for f = 1:numel (fields) |
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110 if (! any (strcmp (fields{f}, |
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111 {"periodic", "robust", "beta", "order", "constraints"}))) |
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112 error ("splinefit:invalidproperty", |
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113 "unrecognized property '%s'", fields{f}); |
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114 endif |
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115 endfor |
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116 args = {}; |
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117 if (isfield (props, "periodic") && props.periodic) |
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118 args{end+1} = "p"; |
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119 endif |
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120 if (isfield (props, "robust") && props.robust) |
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121 args{end+1} = "r"; |
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122 endif |
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123 if (isfield (props, "beta")) |
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124 if (0 < props.beta && props.beta < 1) |
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125 args{end+1} = props.beta; |
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126 else |
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127 error ("splinefit:invalidbeta", "invalid beta parameter (0 < beta < 1)"); |
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128 endif |
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129 endif |
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130 if (isfield (props, "order")) |
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131 if (props.order >= 0) |
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132 args{end+1} = props.order + 1; |
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133 else |
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134 error ("splinefit:invalidorder", "invalid order"); |
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135 endif |
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136 endif |
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137 if (isfield (props, "constraints")) |
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138 args{end+1} = props.constraints; |
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139 endif |
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140 if (nargin < 3) |
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141 print_usage (); |
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142 elseif (! isnumeric (breaks) || ! isvector (breaks)) |
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143 print_usage (); |
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144 endif |
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145 pp = __splinefit__ (x, y, breaks, args{:}); |
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146 endfunction |
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147 |
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148 |
14509 | 149 %!demo |
150 %! % Noisy data | |
151 %! x = linspace (0, 2*pi, 100); | |
152 %! y = sin (x) + 0.1 * randn (size (x)); | |
153 %! % Breaks | |
154 %! breaks = [0:5, 2*pi]; | |
155 %! % Fit a spline of order 5 | |
156 %! pp = splinefit (x, y, breaks, "order", 4); | |
157 %! clf () | |
158 %! plot (x, y, "s", x, ppval (pp, x), "r", breaks, ppval (pp, breaks), "+r") | |
159 %! xlabel ("Independent Variable") | |
160 %! ylabel ("Dependent Variable") | |
161 %! title ("Fit a piece-wise polynomial of order 4"); | |
162 %! legend ({"data", "fit", "breaks"}) | |
163 %! axis tight | |
164 %! ylim auto | |
165 | |
166 %!demo | |
167 %! % Noisy data | |
168 %! x = linspace (0,2*pi, 100); | |
169 %! y = sin (x) + 0.1 * randn (size (x)); | |
170 %! % Breaks | |
171 %! breaks = [0:5, 2*pi]; | |
172 %! % Fit a spline of order 3 with periodic boundary conditions | |
173 %! pp = splinefit (x, y, breaks, "order", 2, "periodic", true); | |
174 %! clf () | |
175 %! plot (x, y, "s", x, ppval (pp, x), "r", breaks, ppval (pp, breaks), "+r") | |
176 %! xlabel ("Independent Variable") | |
177 %! ylabel ("Dependent Variable") | |
178 %! title ("Fit a periodic piece-wise polynomial of order 2"); | |
179 %! legend ({"data", "fit", "breaks"}) | |
180 %! axis tight | |
181 %! ylim auto | |
182 | |
183 %!demo | |
184 %! % Noisy data | |
185 %! x = linspace (0, 2*pi, 100); | |
186 %! y = sin (x) + 0.1 * randn (size (x)); | |
187 %! % Breaks | |
188 %! breaks = [0:5, 2*pi]; | |
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189 %! % Constraints: y(0) = 0, y'(0) = 1 and y(3) + y"(3) = 0 |
14509 | 190 %! xc = [0 0 3]; |
191 %! yc = [0 1 0]; | |
192 %! cc = [1 0 1; 0 1 0; 0 0 1]; | |
193 %! con = struct ("xc", xc, "yc", yc, "cc", cc); | |
194 %! % Fit a cubic spline with 8 pieces and constraints | |
195 %! pp = splinefit (x, y, 8, "constraints", con); | |
196 %! clf () | |
197 %! plot (x, y, "s", x, ppval (pp, x), "r", breaks, ppval (pp, breaks), "+r") | |
198 %! xlabel ("Independent Variable") | |
199 %! ylabel ("Dependent Variable") | |
200 %! title ("Fit a cubic spline with constraints") | |
201 %! legend ({"data", "fit", "breaks"}) | |
202 %! axis tight | |
203 %! ylim auto | |
204 | |
205 %!demo | |
206 %! % Noisy data | |
207 %! x = linspace (0, 2*pi, 100); | |
208 %! y = sin (x) + 0.1 * randn (size (x)); | |
209 %! % Breaks | |
210 %! breaks = [0:5, 2*pi]; | |
211 %! xc = [0 0 3]; | |
212 %! yc = [0 1 0]; | |
213 %! cc = [1 0 1; 0 1 0; 0 0 1]; | |
214 %! con = struct ("xc", xc, "yc", yc, "cc", cc); | |
215 %! % Fit a spline of order 6 with constraints and periodicity | |
216 %! pp = splinefit (x, y, breaks, "constraints", con, "order", 5, "periodic", true); | |
217 %! clf () | |
218 %! plot (x, y, "s", x, ppval (pp, x), "r", breaks, ppval (pp, breaks), "+r") | |
219 %! xlabel ("Independent Variable") | |
220 %! ylabel ("Dependent Variable") | |
221 %! title ("Fit a 5th order piece-wise periodic polynomial with constraints") | |
222 %! legend ({"data", "fit", "breaks"}) | |
223 %! axis tight | |
224 %! ylim auto | |
225 | |
226 %!shared xb, yb, x | |
227 %! xb = 0:2:10; | |
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228 %! yb = 2*rand (size (xb)) - 1; |
14509 | 229 %! x = 0:0.1:10; |
230 | |
231 %!test | |
232 %! y = interp1 (xb, yb, x, "linear"); | |
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233 %! assert (ppval (splinefit (x, y, xb, "order", 1), x), y, 15 * eps ()); |
14509 | 234 %!test |
235 %! y = interp1 (xb, yb, x, "spline"); | |
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236 %! assert (ppval (splinefit (x, y, xb, "order", 3), x), y, 15 * eps ()); |
14509 | 237 %!test |
238 %! y = interp1 (xb, yb, x, "spline"); | |
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239 %! assert (ppval (splinefit (x, y, xb), x), y, 15 * eps ()); |
14509 | 240 |