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annotate m-toolbox/classes/+utils/@math/intfact.m @ 0:f0afece42f48

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Import.
author Daniele Nicolodi <nicolodi@science.unitn.it>
date Wed, 23 Nov 2011 19:22:13 +0100
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Daniele Nicolodi <nicolodi@science.unitn.it>
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1 % INTFACT computes integer factorisation
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2 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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3 %
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4 % INTFACT tries to find two integers, P and Q, that satisfy
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5 %
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6 % y = P/Q * x
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7 %
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Daniele Nicolodi <nicolodi@science.unitn.it>
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8 % >> [p,q] = intfact(y,x)
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9 %
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10 % The following call returns a parameter list object that contains the
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11 % default parameter values:
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12 %
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13 % >> pl = intfact(utils, 'Params')
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14 %
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15 % The following call returns a string that contains the routine CVS version:
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16 %
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17 % >> version = intfact(utils,'Version')
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18 %
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19 % The following call returns a string that contains the routine category:
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20 %
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21 % >> category = intfact(utils,'Category')
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22 %
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23 % VERSION: $Id: intfact.m,v 1.9 2009/02/06 12:03:52 hewitson Exp $
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24 %
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Daniele Nicolodi <nicolodi@science.unitn.it>
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25 % M Hewitson 26-05-08
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26 %
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27 %
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28 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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29
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30 function varargout = intfact(varargin)
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31
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32 % Get input sample rates
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33 fs2 = floor(1e10*varargin{1});
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34 fs1 = floor(1e10*varargin{2});
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35
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36 g = gcd(fs2,fs1);
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37
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38 varargout{1} = fs2/g;
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39 varargout{2} = fs1/g;
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40
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Daniele Nicolodi <nicolodi@science.unitn.it>
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41 return
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42
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43 % Get min and max fs
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44 x = max(fs1,fs2);
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45 y = min(fs1,fs2);
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46
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47 % If we already have two integers then it's easy
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48 if rem(fs2,1) == 0 && rem(fs1,1) == 0
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49 P = fs2;
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50 Q = fs1;
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51 % Get the greatest common divisor
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52 g = gcd(P,Q);
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53 % factor that out
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54 P = P / g;
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55 Q = Q / g;
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56 % If fs1 and fs2 are factors of each other, then it's easy
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57 elseif rem(fs1,fs2) == 0
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58 P = fs1/fs2;
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59 Q = 1;
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60 elseif rem(fs2,fs1) == 0
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61 Q = fs2/fs1;
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62 P = 1;
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63 % Otherwise we search for two integers
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64 else
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65 % Start from N=0
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66 N = 0;
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67 s = x * 10^N;
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68 % Now compute initial P and Q
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69 if fs2 > fs1
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70 P = 10^N;
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71 Q = s / y;
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72 else
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73 Q = 10^N;
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74 P = s / y;
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75 end
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76 % Now look for the integers
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77 while rem(s,1) > 0 || rem(P,1) > 0 || rem(Q,1) > 0
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78 s = x * 10^N;
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79 % Now compute P and Q
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80 if fs2 > fs1
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81 P = 10^N;
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82 Q = s / y;
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83 else
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84 Q = 10^N;
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85 P = s / y;
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86 end
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87 N = N+1;
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88 end
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89
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90 % Get the greatest common divisor
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91 g = gcd(P,Q);
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92
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93 % factor that out
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94 P = P / g;
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95 Q = Q / g;
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96 end
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97
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98 % Set outputs
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99 if nargout == 2
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100 varargout{1} = P;
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101 varargout{2} = Q;
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102 else
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103 error('### Incorrect number of outputs');
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104 end
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105
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106 end
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107 % END