Mercurial > hg > octave-nkf
annotate scripts/general/chop.m @ 20818:9d2023d1a63c
binoinv.m: Implement binary search algorithm for 28X performance increase (bug #34363).
* binoinv.m: Call new functions scalar_binoinv or vector_binoinv to calculate
binoinv. If there are still uncalculated values then call bin_search_binoinv
to perform binary search for remaining values. Add more BIST tests.
* binoinv.m (scalar_binoinv): New subfunction to calculate binoinv for scalar x.
Stops when x > 1000.
* binoinv.m (vector_binoinv): New subfunction to calculate binoinv for scalar x.
Stops when x > 1000.
| author | Lachlan Andrew <lachlanbis@gmail.com> |
|---|---|
| date | Sun, 11 Oct 2015 19:49:40 -0700 |
| parents | 7503499a252b |
| children |
| rev | line source |
|---|---|
|
19898
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maint: Update copyright notices for 2015.
John W. Eaton <jwe@octave.org>
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1 ## Copyright (C) 2010-2015 John W. Eaton |
| 10203 | 2 ## |
| 3 ## This file is part of Octave. | |
| 4 ## | |
| 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. | |
| 9 ## | |
| 10 ## Octave is distributed in the hope that it will be useful, but | |
| 11 ## WITHOUT ANY WARRANTY; without even the implied warranty of | |
| 12 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
| 13 ## General Public License for more details. | |
| 14 ## | |
| 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/>. | |
| 18 | |
| 19 ## -*- texinfo -*- | |
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20 ## @deftypefn {Function File} {} chop (@var{x}, @var{ndigits}, @var{base}) |
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21 ## Truncate elements of @var{x} to a length of @var{ndigits} such that the |
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22 ## resulting numbers are exactly divisible by @var{base}. |
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Rik <rik@octave.org>
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23 ## |
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Rik <rik@octave.org>
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24 ## If @var{base} is not specified it defaults to 10. |
| 10203 | 25 ## |
| 26 ## @example | |
| 27 ## @group | |
| 28 ## chop (-pi, 5, 10) | |
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29 ## @result{} -3.14200000000000 |
| 10203 | 30 ## chop (-pi, 5, 5) |
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31 ## @result{} -3.14150000000000 |
| 10203 | 32 ## @end group |
| 33 ## @end example | |
| 34 ## @end deftypefn | |
| 35 | |
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36 function retval = chop (x, ndigits, base = 10) |
| 10203 | 37 |
| 38 if (nargin == 2 || nargin == 3) | |
| 39 tmp = abs (x); | |
| 40 | |
| 41 ## Avoid computing log (0). | |
| 42 tmp(x == 0) = 1; | |
| 43 | |
| 44 ## Digits to the left of the decimal. | |
| 45 tmp = floor (log10 (tmp) + 1); | |
| 46 | |
| 47 ## The expression | |
| 48 ## | |
| 49 ## round (x .* inflate) | |
| 50 ## | |
| 51 ## produces an integer that contains the digits we want to keep. | |
| 52 ## Multiplying by deflate puts the decimal back where it belngs. | |
| 53 ## | |
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54 ## Further scaling and rounding with the base factor produces a |
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55 ## value with ndigits exactly divisible by base. We skip that step |
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56 ## unless base was explicitly provided. |
| 10203 | 57 |
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58 inflate = 10 .^ (ndigits - tmp); |
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chop.m: Calculate deflate as 1./inflate (bug #43734).
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59 deflate = 1 ./ inflate; |
| 10203 | 60 if (nargin == 2) |
| 61 retval = deflate .* round (x .* inflate); | |
| 62 else | |
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63 retval = base .* deflate .* round (round (x .* inflate) ./ base); |
| 10203 | 64 endif |
| 65 else | |
| 66 print_usage (); | |
| 67 endif | |
| 68 | |
| 69 endfunction | |
| 70 | |
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71 |
| 10203 | 72 %!assert (chop (e, 3), 2.72) |
| 73 %!assert (chop (e, 4), 2.718) | |
| 74 %!assert (chop (e, 4, 5), 2.72) | |
| 75 %!assert (chop (e, 4, 7), 2.716) | |
| 76 %!assert (chop (-e, 3), -2.72) | |
| 77 %!assert (chop (-e, 4), -2.718) | |
| 78 %!assert (chop (-e, 4, 5), -2.72) | |
| 79 %!assert (chop (-e, 4, 7), -2.716) | |
| 80 %!assert (chop (hilb (3), 3), [1,.5,.333;.5,.333,.25;.333,.25,.2]) | |
| 81 %!assert (chop (hilb (3), 2, 7), [.7,.49,.35;.49,.35,.28;.35,.28,.21], 2*eps) | |
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Use Octave coding conventions in all m-file %!test blocks
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82 |