## Mercurial > hg > octave-max

### view scripts/general/chop.m @ 15489:481417a57a2d

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improve sign and signbit docs
* mappers.cc (Fsign): Note sign (-0) is 0. Add @seealso for signbit.
(Fsignbit): Add @seealso for sign.

author | John W. Eaton <jwe@octave.org> |
---|---|

date | Thu, 04 Oct 2012 10:20:59 -0400 |

parents | f3d52523cde1 |

children |

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## Copyright (C) 2010-2012 John W. Eaton ## ## 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 {Function File} {} chop (@var{x}, @var{ndigits}, @var{base}) ## Truncate elements of @var{x} to a length of @var{ndigits} such that the ## resulting numbers are exactly divisible by @var{base}. If @var{base} is not ## specified it defaults to 10. ## ## @example ## @group ## chop (-pi, 5, 10) ## @result{} -3.14200000000000 ## chop (-pi, 5, 5) ## @result{} -3.14150000000000 ## @end group ## @end example ## @end deftypefn function retval = chop (x, ndigits, base = 10) if (nargin == 2 || nargin == 3) tmp = abs (x); ## Avoid computing log (0). tmp(x == 0) = 1; ## Digits to the left of the decimal. tmp = floor (log10 (tmp) + 1); ## The expression ## ## round (x .* inflate) ## ## produces an integer that contains the digits we want to keep. ## Multiplying by deflate puts the decimal back where it belngs. ## ## Further scaling and rounding with the base factor produces a ## value with ndigits exactly divisible by base. We skip that step ## unless base was explicitly provided. inflate = 10 .^ (ndigits - tmp); deflate = 10 .^ (tmp - ndigits); if (nargin == 2) retval = deflate .* round (x .* inflate); else retval = base .* deflate .* round (round (x .* inflate) ./ base); endif else print_usage (); endif endfunction %!assert (chop (e, 3), 2.72) %!assert (chop (e, 4), 2.718) %!assert (chop (e, 4, 5), 2.72) %!assert (chop (e, 4, 7), 2.716) %!assert (chop (-e, 3), -2.72) %!assert (chop (-e, 4), -2.718) %!assert (chop (-e, 4, 5), -2.72) %!assert (chop (-e, 4, 7), -2.716) %!assert (chop (hilb (3), 3), [1,.5,.333;.5,.333,.25;.333,.25,.2]) %!assert (chop (hilb (3), 2, 7), [.7,.49,.35;.49,.35,.28;.35,.28,.21], 2*eps)