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1 ## Copyright (C) 1996, 1998, 2000 Auburn University. All rights reserved. |
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2 ## |
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3 ## This file is part of Octave. |
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4 ## |
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5 ## Octave is free software; you can redistribute it and/or modify it |
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6 ## under the terms of the GNU General Public License as published by the |
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7 ## Free Software Foundation; either version 2, or (at your option) any |
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8 ## later version. |
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9 ## |
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10 ## Octave is distributed in the hope that it will be useful, but WITHOUT |
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11 ## ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
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12 ## FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
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13 ## for more details. |
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14 ## |
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15 ## You should have received a copy of the GNU General Public License |
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16 ## along with Octave; see the file COPYING. If not, write to the Free |
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17 ## Software Foundation, 59 Temple Place, Suite 330, Boston, MA 02111 USA. |
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18 |
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19 ## -*- texinfo -*- |
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20 ## @deftypefn {Function File} {} sysprune (@var{asys}, @var{out_idx}, @var{in_idx}) |
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21 ## Extract specified inputs/outputs from a system |
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22 ## |
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23 ## @strong{Inputs} |
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24 ## @table @var |
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25 ## @item asys |
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26 ## system data structure |
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27 ## @item out_idx |
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28 ## @itemx in_idx |
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29 ## |
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30 ## Indices or signal names of the outputs and inputs to be kept in the returned |
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31 ## system; remaining connections are "pruned" off. |
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32 ## May select as [] (empty matrix) to specify all outputs/inputs. |
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33 ## |
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34 ## @example |
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35 ## retsys = sysprune(Asys,[1:3,4],"u_1"); |
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36 ## retsys = sysprune(Asys,list("tx","ty","tz"), 4); |
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37 ## @end example |
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38 ## |
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39 ## @end table |
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40 ## |
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41 ## @strong{Outputs} |
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42 ## @var{retsys}: resulting system |
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43 ## @example |
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44 ## @group |
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45 ## ____________________ |
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46 ## u1 ------->| |----> y1 |
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47 ## (in_idx) | Asys | (out_idx) |
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48 ## u2 ------->| |----| y2 |
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49 ## (deleted)-------------------- (deleted) |
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50 ## @end group |
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51 ## @end example |
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52 ## @end deftypefn |
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53 |
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54 ## Author: A. S. Hodel <a.s.hodel@eng.auburn.edu> |
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55 ## Created: August 1995 |
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56 ## Updated by John Ingram 7-15-96 |
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57 |
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58 function sys = sysprune (sys, output_idx, input_idx, state_idx) |
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59 |
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60 if( nargin < 3 | nargin > 4 ) |
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61 usage("retsys = sysprune(sys,output_idx,input_idx{,state_idx})"); |
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62 elseif(nargin < 4) |
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63 state_idx = []; |
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64 endif |
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65 |
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66 ## default: no action |
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67 [nn,nz,mm,pp] = sysdimensions(sys); |
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68 if(isempty(output_idx)) output_idx = 1:pp; endif |
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69 if(isempty(input_idx)) input_idx = 1:mm; endif |
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70 if(isempty(state_idx)) state_idx = 1:(nn+nz); endif |
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71 |
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72 ## check for signal names |
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73 if(is_signal_list(output_idx) | isstr(output_idx)) |
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74 output_idx = sysidx(sys,"out",output_idx); |
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75 endif |
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76 if(is_signal_list(input_idx) | isstr(input_idx)) |
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77 input_idx = sysidx(sys,"in",input_idx); |
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78 endif |
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79 |
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80 ## check dimensions |
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81 if( !(isvector(output_idx) | isempty(output_idx) ) ) |
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82 if(!ismatrix(output_idx)) |
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83 error("sysprune: bad argument passed for output_idx"); |
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84 else |
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85 error("sysprune: output_idx (%d x %d) must be a vector or empty", ... |
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86 rows(output_idx),columns(output_idx)); |
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87 endif |
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88 elseif(is_duplicate_entry(output_idx)) |
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89 error("sysprune: duplicate entries found in output_idx"); |
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90 endif |
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91 |
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92 if( !(isvector(input_idx) | isempty(input_idx) ) ) |
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93 if(!ismatrix(input_idx)) |
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94 error("sysprune: bad argument passed for input_idx"); |
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95 else |
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96 error("sysprune: input_idx (%d x %d) must be a vector or empty", ... |
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97 rows(input_idx),columns(input_idx)); |
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98 endif |
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99 elseif(is_duplicate_entry(input_idx)) |
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100 error("sysprune: duplicate entries found in input_idx"); |
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101 endif |
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102 |
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103 if( !(isvector(state_idx) | isempty(state_idx) ) ) |
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104 if(!ismatrix(state_idx)) |
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105 error("sysprune: bad argument passed for state_idx"); |
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106 else |
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107 error("sysprune: state_idx (%d x %d) must be a vector or empty", ... |
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108 rows(state_idx),columns(state_idx)); |
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109 endif |
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110 elseif(nn+nz > 0) |
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111 if(is_duplicate_entry(state_idx)) |
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112 error("sysprune: duplicate entries found in state_idx"); |
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113 endif |
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114 endif |
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115 |
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116 lo = length(output_idx); |
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117 li = length(input_idx); |
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118 lst = length(state_idx); |
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119 |
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120 if( !isstruct(sys)) |
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121 error("Asys must be a system data structure (see ss, tf, or zp)") |
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122 elseif(pp < lo) |
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123 error([num2str(lo)," output_idx entries, system has only ", ... |
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124 num2str(pp)," outputs"]); |
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125 elseif(mm < li) |
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126 error([num2str(li)," input_idx entries, system has only ", ... |
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127 num2str(mm)," inputs"]); |
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128 elseif(nn+nz < lst) |
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129 error([num2str(lst)," state_idx entries, system has only ", ... |
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130 num2str(nn+nz)," states"]); |
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131 endif |
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132 |
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133 [aa,bb,cc,dd,tsam,nn,nz,stnam,innam,outnam,yd] = sys2ss(sys); |
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134 |
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135 ## check for valid state permutation |
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136 if(nn & nz) |
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137 c_idx = find(state_idx <= nn); |
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138 if(!isempty(c_idx)) max_c = max(c_idx); |
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139 else max_c = 0; endif |
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140 d_idx = find(state_idx > nn); |
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141 if(!isempty(d_idx)) min_d = min(d_idx); |
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142 else min_d = nn+nz; endif |
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143 if(max_c > min_d) |
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144 warning("sysprune: state_idx(%d)=%d (discrete) preceeds", ... |
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145 min_d,state_idx(min_d)); |
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146 warning(" state_idx(%d)=%d (continuous)",... |
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147 max_c,state_idx(max_c)); |
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148 warning("sysprune: sys has %d continuous states, %d discrete states", ... |
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149 nn,nz); |
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150 error("continuous/discrete state partition not preserved ; see ss"); |
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151 endif |
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152 endif |
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153 |
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154 idx = input_idx; |
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155 odx = output_idx; |
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156 if(isempty(state_idx)) |
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157 idx = []; |
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158 odx = []; |
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159 endif |
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160 aa = aa(state_idx,state_idx); |
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161 bb = bb(state_idx,idx); |
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162 cc = cc(odx,state_idx); |
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163 dd = dd(output_idx,input_idx); |
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164 yd = yd(output_idx); |
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165 |
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166 innam = innam(input_idx); |
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167 outnam = outnam(output_idx); |
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168 stnam = stnam(state_idx); |
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169 nn1 = length(find(state_idx <= nn)); |
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170 nz1 = length(find(state_idx > nn)); |
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171 sys = ss(aa,bb,cc,dd,tsam,nn1,nz1,stnam,innam,outnam,find(yd)); |
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172 endfunction |
