Mercurial > octave
view scripts/general/interpft.m @ 21317:a4faec57f4c8
maint: remove semicolon after %!assert tests to follow Octave conventions.
* testfun.txi: Remove semicolons from examples in manual and update remaider
of text to reflect changes.
* bsxfun.cc, cellfun.cc, data.cc, hash.cc, lu.cc, nproc.cc,
rcond.cc, regexp.cc, sparse-xpow.cc, strfns.cc, symtab.cc, time.cc,
variables.cc, ov-class.cc, ov-cx-diag.cc, ov-struct.cc, ov.cc, oct-parse.in.yy,
pt-mat.cc, CMatrix.cc, oct-inttypes.cc, md5sum.m, blkdiag.m, cell2mat.m,
interp1.m, interp2.m, interpft.m, num2str.m, repmat.m, ntsc2rgb.m, expm.m,
inputname.m, polyvalm.m, blackman.m, hamming.m, hanning.m, eigs.m, median.m,
binopdf.m, strsplit.m, strtok.m, assert.m, example.m, datevec.m, bug-38565.tst,
build-sparse-tests.sh, classdef.tst, classes.tst, diag-perm.tst, index.tst,
io.tst, logical-index.tst, nest.tst, parser.tst, prefer.tst, struct.tst:
maint: remove semicolon after %!assert tests to follow Octave conventions.
author | Rik <rik@octave.org> |
---|---|
date | Sun, 21 Feb 2016 08:10:36 -0800 |
parents | 516bb87ea72e |
children | bac0d6f07a3e |
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## Copyright (C) 2001-2015 Paul Kienzle ## ## This file is part of Octave. ## ## Octave is free software; you can redistribute it and/or modify it ## under the terms of the GNU General Public License as published by ## the Free Software Foundation; either version 3 of the License, or (at ## your option) any later version. ## ## Octave is distributed in the hope that it will be useful, but ## WITHOUT ANY WARRANTY; without even the implied warranty of ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU ## General Public License for more details. ## ## You should have received a copy of the GNU General Public License ## along with Octave; see the file COPYING. If not, see ## <http://www.gnu.org/licenses/>. ## -*- texinfo -*- ## @deftypefn {} {} interpft (@var{x}, @var{n}) ## @deftypefnx {} {} interpft (@var{x}, @var{n}, @var{dim}) ## ## Fourier interpolation. ## ## If @var{x} is a vector then @var{x} is resampled with @var{n} points. The ## data in @var{x} is assumed to be equispaced. If @var{x} is a matrix or an ## N-dimensional array, the interpolation is performed on each column of ## @var{x}. ## ## If @var{dim} is specified, then interpolate along the dimension @var{dim}. ## ## @code{interpft} assumes that the interpolated function is periodic, and so ## assumptions are made about the endpoints of the interpolation. ## @seealso{interp1} ## @end deftypefn ## Author: Paul Kienzle ## 2001-02-11 ## * initial version ## 2002-03-17 aadler ## * added code to work on matrices as well ## 2006-05-25 dbateman ## * Make it matlab compatiable, cutting out the 2-D interpolation function z = interpft (x, n, dim) if (nargin < 2 || nargin > 3) print_usage (); endif if (! (isscalar (n) && n == fix (n))) error ("interpft: N must be a scalar integer"); endif if (nargin == 2) if (isrow (x)) dim = 2; else dim = 1; endif endif nd = ndims (x); if (dim < 1 || dim > nd) error ("interpft: invalid dimension DIM"); endif perm = [dim:nd, 1:(dim-1)]; x = permute (x, perm); m = rows (x); inc = ceil (m/n); y = fft (x) / m; k = ceil (m / 2); sz = size (x); sz(1) = n * inc - m; idx = repmat ({':'}, nd, 1); idx{1} = 1:k; z = cat (1, y(idx{:}), zeros (sz)); idx{1} = k+1:m; z = cat (1, z, y(idx{:})); ## When m is an even number of rows, the FFT has a single Nyquist bin. ## If zero-padded above, distribute the value of the Nyquist bin evenly ## between the new corresponding positive and negative frequency bins. if (sz(1) > 0 && k == m/2) idx{1} = n * inc - k + 1; tmp = z(idx{:}) / 2; z(idx{:}) = tmp; idx{1} = k + 1; z(idx{:}) = tmp; endif z = n * ifft (z); if (inc != 1) sz(1) = n; z = inc * reshape (z(1:inc:end), sz); endif z = ipermute (z, perm); endfunction %!demo %! clf; %! t = 0 : 0.3 : pi; dt = t(2)-t(1); %! n = length (t); k = 100; %! ti = t(1) + [0 : k-1]*dt*n/k; %! y = sin (4*t + 0.3) .* cos (3*t - 0.1); %! yp = sin (4*ti + 0.3) .* cos (3*ti - 0.1); %! plot (ti, yp, 'g', ti, interp1(t, y, ti, "spline"), 'b', ... %! ti, interpft (y, k), 'c', t, y, "r+"); %! legend ("sin(4t+0.3)cos(3t-0.1)", "spline", "interpft", "data"); %!shared n,y %! x = [0:10]'; y = sin(x); n = length (x); %!assert (interpft (y, n), y, 20*eps) %!assert (interpft (y', n), y', 20*eps) %!assert (interpft ([y,y],n), [y,y], 20*eps) ## Test case with complex input from bug #39566 %!test %! x = (1 + j) * [1:4]'; %! y = ifft ([15 + 15*j; -6; -1.5 - 1.5*j; 0; -1.5 - 1.5*j; -6*j]); %! assert (interpft (x, 6), y, 10*eps); ## Test for correct spectral symmetry with even/odd lengths %!assert (max (abs (imag (interpft ([1:8], 20)))), 0, 20*eps) %!assert (max (abs (imag (interpft ([1:8], 21)))), 0, 21*eps) %!assert (max (abs (imag (interpft ([1:9], 20)))), 0, 20*eps) %!assert (max (abs (imag (interpft ([1:9], 21)))), 0, 21*eps) ## Test input validation %!error interpft () %!error interpft (1) %!error interpft (1,2,3) %!error <N must be a scalar integer> interpft (1,[2,2]) %!error <N must be a scalar integer> interpft (1,2.1) %!error <invalid dimension DIM> interpft (1,2,0) %!error <invalid dimension DIM> interpft (1,2,3)