Mercurial > hg > octave-nkf
annotate scripts/sparse/sprand.m @ 12749:e7cc2d4a6db3 stable
Fix range of sigma in normal distribution to exclude 0.
* normcdf.m, normpdf.m: Correct 's >= 0' to 's > 0'.
author | Rik <octave@nomad.inbox5.com> |
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date | Thu, 16 Jun 2011 21:05:10 -0700 |
parents | c792872f8942 |
children | 63d06af0376a |
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11523 | 1 ## Copyright (C) 2004-2011 Paul Kienzle |
5164 | 2 ## |
7016 | 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 ## Original version by Paul Kienzle distributed as free software in the | |
20 ## public domain. | |
5164 | 21 |
22 ## -*- texinfo -*- | |
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23 ## @deftypefn {Function File} {} sprand (@var{m}, @var{n}, @var{d}) |
5164 | 24 ## @deftypefnx {Function File} {} sprand (@var{s}) |
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25 ## Generate a random sparse matrix. The size of the matrix will be |
5164 | 26 ## @var{m} by @var{n}, with a density of values given by @var{d}. |
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27 ## @var{d} should be between 0 and 1. Values will be uniformly |
5610 | 28 ## distributed between 0 and 1. |
5164 | 29 ## |
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30 ## Note: sometimes the actual density may be a bit smaller than @var{d}. |
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31 ## This is unlikely to happen for large, truly sparse, matrices. |
5164 | 32 ## |
33 ## If called with a single matrix argument, a random sparse matrix is | |
34 ## generated wherever the matrix @var{S} is non-zero. | |
5642 | 35 ## @seealso{sprandn} |
5164 | 36 ## @end deftypefn |
37 | |
38 ## Author: Paul Kienzle <pkienzle@users.sf.net> | |
39 ## | |
40 ## Changelog: | |
41 ## | |
42 ## Piotr Krzyzanowski <przykry2004@users.sf.net> | |
10549 | 43 ## 2004-09-27 use Paul's hint to allow larger random matrices |
44 ## at the price of sometimes lower density than desired | |
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45 ## David Bateman |
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46 ## 2004-10-20 Texinfo help and copyright message |
5164 | 47 |
48 function S = sprand (m, n, d) | |
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49 |
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50 if (nargin != 1 && nargin != 3) |
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51 print_usage (); |
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52 endif |
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53 |
6498 | 54 if (nargin == 1) |
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55 [i, j, v] = find (m); |
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56 [nr, nc] = size (m); |
6498 | 57 S = sparse (i, j, rand (size (v)), nr, nc); |
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58 return; |
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59 endif |
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60 |
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61 if (!(isscalar (m) && m == fix (m) && m > 0)) |
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62 error ("sprand: M must be an integer greater than 0"); |
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63 endif |
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64 |
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65 if (!(isscalar (n) && n == fix (n) && n > 0)) |
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66 error ("sprand: N must be an integer greater than 0"); |
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67 endif |
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68 |
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69 if (d < 0 || d > 1) |
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70 error ("sprand: density D must be between 0 and 1"); |
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71 endif |
6498 | 72 |
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73 mn = m*n; |
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74 ## how many entries in S would be satisfactory? |
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75 k = round (d*mn); |
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76 idx = unique (fix (rand (min (k*1.01, k+10), 1) * mn)) + 1; |
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77 ## idx contains random numbers in [1,mn] |
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78 ## generate 1% or 10 more random values than necessary in order to |
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79 ## reduce the probability that there are less than k distinct |
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80 ## values; maybe a better strategy could be used but I don't think |
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81 ## it's worth the price |
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82 |
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83 ## actual number of entries in S |
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84 k = min (length (idx), k); |
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85 j = floor ((idx(1:k)-1)/m); |
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86 i = idx(1:k) - j*m; |
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87 if (isempty (i)) |
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88 S = sparse (m, n); |
5164 | 89 else |
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90 S = sparse (i, j+1, rand (k, 1), m, n); |
5164 | 91 endif |
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92 |
5164 | 93 endfunction |
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94 |