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1 % PROCESS_OPTIONS - Processes options passed to a Matlab function.
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2 % This function provides a simple means of
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3 % parsing attribute-value options. Each option is
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4 % named by a unique string and is given a default
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5 % value.
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6 %
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7 % Usage: [var1, var2, ..., varn[, unused]] = ...
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8 % process_options(args, ...
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9 % str1, def1, str2, def2, ..., strn, defn)
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10 %
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11 % Arguments:
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12 % args - a cell array of input arguments, such
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13 % as that provided by VARARGIN. Its contents
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14 % should alternate between strings and
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15 % values.
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16 % str1, ..., strn - Strings that are associated with a
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17 % particular variable
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18 % def1, ..., defn - Default values returned if no option
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19 % is supplied
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20 %
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21 % Returns:
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22 % var1, ..., varn - values to be assigned to variables
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23 % unused - an optional cell array of those
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24 % string-value pairs that were unused;
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25 % if this is not supplied, then a
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26 % warning will be issued for each
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27 % option in args that lacked a match.
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28 %
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29 % Examples:
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30 %
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31 % Suppose we wish to define a Matlab function 'func' that has
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32 % required parameters x and y, and optional arguments 'u' and 'v'.
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33 % With the definition
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34 %
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35 % function y = func(x, y, varargin)
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36 %
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37 % [u, v] = process_options(varargin, 'u', 0, 'v', 1);
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38 %
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39 % calling func(0, 1, 'v', 2) will assign 0 to x, 1 to y, 0 to u, and 2
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40 % to v. The parameter names are insensitive to case; calling
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41 % func(0, 1, 'V', 2) has the same effect. The function call
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42 %
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43 % func(0, 1, 'u', 5, 'z', 2);
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44 %
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45 % will result in u having the value 5 and v having value 1, but
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46 % will issue a warning that the 'z' option has not been used. On
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47 % the other hand, if func is defined as
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48 %
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49 % function y = func(x, y, varargin)
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50 %
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51 % [u, v, unused_args] = process_options(varargin, 'u', 0, 'v', 1);
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52 %
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53 % then the call func(0, 1, 'u', 5, 'z', 2) will yield no warning,
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54 % and unused_args will have the value {'z', 2}. This behaviour is
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55 % useful for functions with options that invoke other functions
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56 % with options; all options can be passed to the outer function and
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57 % its unprocessed arguments can be passed to the inner function.
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58
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59 % Copyright (C) 2002 Mark A. Paskin
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60 %
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61 % This program is free software; you can redistribute it and/or modify
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62 % it under the terms of the GNU General Public License as published by
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63 % the Free Software Foundation; either version 2 of the License, or
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64 % (at your option) any later version.
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65 %
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66 % This program is distributed in the hope that it will be useful, but
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67 % WITHOUT ANY WARRANTY; without even the implied warranty of
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68 % MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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69 % General Public License for more details.
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70 %
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71 % You should have received a copy of the GNU General Public License
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72 % along with this program; if not, write to the Free Software
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73 % Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
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74 % USA.
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75 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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76
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77 function [varargout] = process_options(args, varargin)
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78
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79 % Check the number of input arguments
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80 n = length(varargin);
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81 if (mod(n, 2))
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82 error('Each option must be a string/value pair.');
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83 end
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84
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85 % Check the number of supplied output arguments
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86 if (nargout < (n / 2))
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87 error('Insufficient number of output arguments given');
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88 elseif (nargout == (n / 2))
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89 warn = 1;
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90 nout = n / 2;
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91 else
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92 warn = 0;
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93 nout = n / 2 + 1;
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94 end
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95
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96 % Set outputs to be defaults
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97 varargout = cell(1, nout);
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98 for i=2:2:n
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99 varargout{i/2} = varargin{i};
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100 end
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101
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102 % Now process all arguments
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103 nunused = 0;
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104 for i=1:2:length(args)
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105 found = 0;
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106 for j=1:2:n
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107 if strcmpi(args{i}, varargin{j})
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108 varargout{(j + 1)/2} = args{i + 1};
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109 found = 1;
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110 break;
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111 end
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112 end
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113 if (~found)
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114 if (warn)
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115 warning(sprintf('Option ''%s'' not used.', args{i}));
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116 args{i}
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117 else
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118 nunused = nunused + 1;
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119 unused{2 * nunused - 1} = args{i};
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120 unused{2 * nunused} = args{i + 1};
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121 end
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122 end
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123 end
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124
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125 % Assign the unused arguments
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126 if (~warn)
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127 if (nunused)
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128 varargout{nout} = unused;
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129 else
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130 varargout{nout} = cell(0);
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131 end
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132 end
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