1 ## Copyright (C) 2008-2012 David Bateman
3 ## This file is part of Octave.
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.
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12 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 ## General Public License for more details.
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/>.
20 ## @deftypefn {Function File} {@var{yi} =} interp1q (@var{x}, @var{y}, @var{xi})
21 ## One-dimensional linear interpolation without error checking.
22 ## Interpolates @var{y}, defined at the points @var{x}, at the points
23 ## @var{xi}. The sample points @var{x} must be a strictly monotonically
24 ## increasing column vector. If @var{y} is an array, treat the columns
25 ## of @var{y} separately. If @var{y} is a vector, it must be a column
26 ## vector of the same length as @var{x}.
28 ## Values of @var{xi} beyond the endpoints of the interpolation result
29 ## in NA being returned.
31 ## Note that the error checking is only a significant portion of the
32 ## execution time of this @code{interp1} if the size of the input arguments
33 ## is relatively small. Therefore, the benefit of using @code{interp1q}
34 ## is relatively small.
38 function yi = interp1q (x, y, xi)
48 idx = lookup (x, xi, "lr");
49 s = (xi - x (idx)) ./ dx (idx);
50 yi = bsxfun (@times, s, dy(idx,:)) + y(idx,:);
51 range = xi < x(1) | !(xi <= x(nx));
53 if (length (szx) == 2 && any (szx == 1))
54 yi = reshape (yi, [max(szx), szy(2:end)]);
56 yi = reshape (yi, [szx, szy(2:end)]);
60 %!shared xp, yp, xi, yi
61 %! xp=[0:2:10].'; yp = sin(2*pi*xp/5);
62 %! xi = [-1; 0; 2.2; 4; 6.6; 10; 11];
63 %! yi = interp1 (xp,yp,xi);
64 %!assert (interp1q(xp, yp, [min(xp)-1; max(xp)+1]), [NA; NA]);
65 %!assert (interp1q(xp,yp,xp), yp, 100*eps);
66 %!assert (isempty(interp1q(xp,yp,[])));
67 %!assert (interp1q(xp,yp,xi), yi);
68 %!assert (interp1q(xp,[yp,yp],xi), [yi, yi]);
69 %!assert (interp1q(xp,yp,[xi,xi]), [yi, yi]);
70 %!assert (interp1q(xp,[yp,yp],[xi,xi]), cat (3, [yi, yi], [yi, yi]));