Mercurial > octave-antonio
view scripts/specfun/nthroot.m @ 19117:a4c226a963c5
Deprecate finite in favor of isfinite.
* NEWS: Announce change.
* mappers.cc: Remove DEFALIAS of finite to isfinite. Replace finite with
isfinite in %!tests.
* scripts/deprecated/finite.m: New m-file script to replace C++ DEFALIAS.
* scripts/deprecated/module.mk: Add finite.m to build system.
* cosd.m, sind.m, tand.m, nthroot.m: Replace occurrences of finite with
isfinite in core m-files.
author | Rik <rik@octave.org> |
---|---|
date | Sat, 20 Sep 2014 20:20:41 -0700 |
parents | bb20384acf7b |
children | 238522618904 |
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## Copyright (C) 2004-2013 Paul Kienzle ## Copyright (C) 2010 VZLU Prague ## ## 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/>. ## ## Original version by Paul Kienzle distributed as free software in the ## public domain. ## -*- texinfo -*- ## @deftypefn {Function File} {} nthroot (@var{x}, @var{n}) ## ## Compute the real (non-complex) @var{n}-th root of @var{x}. ## ## @var{x} must have all real entries and @var{n} must be a scalar. ## If @var{n} is an even integer and @var{x} has negative entries then ## @code{nthroot} aborts and issues an error. ## ## Example: ## ## @example ## @group ## nthroot (-1, 3) ## @result{} -1 ## (-1) ^ (1 / 3) ## @result{} 0.50000 - 0.86603i ## @end group ## @end example ## @seealso{realsqrt, sqrt, cbrt} ## @end deftypefn function y = nthroot (x, n) if (nargin != 2) print_usage (); endif if (iscomplex (x)) error ("nthroot: X must not contain complex values"); endif if (! isreal (n) || ! isscalar (n) || n == 0) error ("nthroot: N must be a real nonzero scalar"); endif if (n == 3) y = cbrt (x); elseif (n == -3) y = 1 ./ cbrt (x); elseif (n < 0) y = 1 ./ nthroot (x, -n); else ## Compute using power. integer_n = n == fix (n); if (integer_n && mod (n, 2) == 1) y = abs (x) .^ (1/n) .* sign (x); elseif (any (x(:) < 0)) error ("nthroot: N must be an odd integer if X contains negative values"); else y = x .^ (1/n); endif if (integer_n && n > 0 && isfinite (n)) ## FIXME: What is this correction for? y = ((n-1)*y + x ./ (y.^(n-1))) / n; y = merge (isfinite (y), y, x); endif endif endfunction %!assert (nthroot (-32, 5), -2) %!assert (nthroot (81, 4), 3) %!assert (nthroot (Inf, 4), Inf) %!assert (nthroot (-Inf, 7), -Inf) %!assert (nthroot (-Inf, -7), 0) %% Test input validation %!error nthroot () %!error nthroot (1) %!error nthroot (1,2,3) %!error <X must not contain complex values> nthroot (1+j, 2) %!error <N must be a real nonzero scalar> nthroot (1, i) %!error <N must be a real nonzero scalar> nthroot (1, [1 2]) %!error <N must be a real nonzero scalar> nthroot (1, 0) %!error <N must be an odd integer> nthroot (-1, 2)