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1 ## Copyright (C) 2008 David Bateman |
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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} =} interp1q (@var{x}, @var{y}, @var{xi}) |
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21 ## One-dimensional linear interpolation without error checking. |
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22 ## Interpolates @var{y}, defined at the points @var{x}, at the points |
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23 ## @var{xi}. The sample points @var{x} must be a strictly monotonically |
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24 ## increasing column vector. If @var{y} is an array, treat the columns |
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25 ## of @var{y} separately. If @var{y} is a vector, it must be a column |
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26 ## vector of the same length as @var{x}. |
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27 ## |
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28 ## Values of @var{xi} beyond the endpoints of the interpolation result |
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29 ## in NA being returned. |
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30 ## |
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31 ## Note that the error checking is only a significant portion of the |
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32 ## execution time of this @code{interp1} if the size of the input arguments |
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33 ## is relatively small. Therefore, the benefit of using @code{interp1q} |
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34 ## is relatively small. |
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35 ## @seealso{interp1} |
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36 ## @end deftypefn |
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37 |
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38 function yi = interp1q (x, y, xi) |
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39 x = x(:); |
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40 nx = size (x, 1); |
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41 szy = size (y); |
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42 ny = szy (1); |
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43 nc = prod (szy (2 : end)); |
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44 y = reshape (y, ny, nc); |
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45 szx = size (xi); |
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46 xi = xi (:); |
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47 range = find (xi >= x (1) & xi <= x (nx)); |
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48 yi = NA (size(xi, 1), size (y, 2)); |
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49 xi = xi (range); |
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50 dy = y (2 : ny, :) - y (1 : ny - 1, :); |
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51 dx = x (2 : nx) - x (1 : nx - 1); |
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52 idx = lookup (x, xi, "lr"); |
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53 s = (xi - x (idx)) ./ dx (idx); |
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54 yi (range, :) = s (:, ones (1, nc)) .* dy (idx, :) + y (idx, :); |
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55 if (length (szx) == 2 && any (szx == 1)) |
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56 yi = reshape (yi, [max (szx), szy (2 : end)]); |
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57 else |
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58 yi = reshape (yi, [szx, szy(2:end)]); |
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59 endif |
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60 endfunction |
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61 |
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62 %!shared xp, yp, xi |
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63 %! xp=[0:2:10].'; yp = sin(2*pi*xp/5); |
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64 %! xi = [-1; 0; 2.2; 4; 6.6; 10; 11]; |
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65 %!assert (interp1(xp, yp, [min(xp)-1; max(xp)+1]), [NA; NA]); |
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66 %!assert (interp1(xp,yp,xp), yp, 100*eps); |
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67 %!assert (isempty(interp1(xp,yp,[]))); |
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68 %!assert (interp1(xp,[yp,yp],xi), [interp1(xp,yp,xi),interp1(xp,yp,xi)]); |
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69 %!assert (interp1(xp,yp,[xi,xi]), [interp1(xp,yp,xi),interp1(xp,yp,xi)]); |
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70 %!assert (interp1(xp,[yp,yp],[xi,xi]), [interp1(xp,yp,xi),interp1(xp,yp,xi)]); |
