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improve Matlab compatibility & performance of ppval/mkpp and some associated funcs
author Jaroslav Hajek <highegg@gmail.com>
date Mon, 02 Nov 2009 14:04:06 +0100
parents eb63fbe60fab
children fbd7843974fa
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eb63fbe60fab update copyright notices
John W. Eaton <jwe@octave.org>
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1 ## Copyright (C) 2000, 2006, 2007, 2008 Paul Kienzle
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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 3 of the License, or (at
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8 ## your option) 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, see
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17 ## <http://www.gnu.org/licenses/>.
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18
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19 ## -*- texinfo -*-
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20 ## @deftypefn {Function File} {@var{yi} =} ppval (@var{pp}, @var{xi})
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21 ## Evaluate piece-wise polynomial @var{pp} at the points @var{xi}.
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22 ## If @var{pp} is scalar-valued, the result is an array of the same shape as @var{xi}.
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23 ## Otherwise, the size of the result is @code{[pp.d, length(@var{xi})]} if
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24 ## @var{xi} is a vector, or @code{[pp.d, size(@var{xi})]} if it is a multi-dimensional
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25 ## array. If pp.orient is 1, the dimensions are permuted as in interp1, to
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26 ## @code{[pp.d, length(@var{xi})]} and @code{[pp.d, size(@var{xi})]} respectively.
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27 ## @seealso{mkpp, unmkpp, spline}
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28 ## @end deftypefn
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29
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30 function yi = ppval (pp, xi)
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31
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32 if (nargin != 2)
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33 print_usage ();
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34 endif
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35 if (! isstruct (pp))
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36 error ("ppval: expects a pp structure");
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37 endif
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38
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39 ## Extract info.
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40 x = pp.x;
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41 P = pp.P;
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42 d = pp.d;
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43 k = size (P, 3);
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44 nd = size (P, 1);
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45
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46 ## Determine resulting shape.
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47 if (d == 1) # scalar case
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48 yisz = size (xi);
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49 elseif (isvector (xi)) # this is special
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50 yisz = [d, length(xi)];
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51 else # general
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52 yisz = [d, size(xi)];
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53 endif
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54
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55 ## Determine intervals.
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56 xi = xi(:);
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57 xn = numel (xi);
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58
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59 idx = lookup (x, xi, "lr");
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60
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61 ## Offsets.
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62 dx = (xi - x(idx)).';
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63 dx = dx(ones (1, nd), :); # spread (do nothing in 1D)
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64
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65 ## Use Horner scheme.
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66 yi = P(:,idx,1);
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67 for i = 2:k;
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68 yi .*= dx;
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69 yi += P(:,idx,i);
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70 endfor
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71
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72 ## Adjust shape.
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73 yi = reshape (yi, yisz);
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74 if (d != 1 && pp.orient == 1)
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75 ## Switch dimensions to match interp1 order.
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76 yi = shiftdim (yi, length (d));
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77 endif
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78
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79 endfunction