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1 ## Copyright (C) 1996 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 |
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7 ## the Free Software Foundation; either version 3 of the License, or (at |
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8 ## your option) any later version. |
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9 ## |
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10 ## Octave is distributed in the hope that it will be useful, but |
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11 ## WITHOUT ANY WARRANTY; without even the implied warranty of |
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12 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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13 ## General Public License 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, see |
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17 ## <http://www.gnu.org/licenses/>. |
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18 |
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19 ## -*- texinfo -*- |
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20 ## @deftypefn {Function File} {@var{out} =} ltifr (@var{a}, @var{b}, @var{w}) |
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21 ## @deftypefnx {Function File} {@var{out} =} ltifr (@var{sys}, @var{w}) |
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22 ## Linear time invariant frequency response of single-input systems. |
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23 ## |
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24 ## @strong{Inputs} |
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25 ## @table @var |
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26 ## @item a |
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27 ## @itemx b |
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28 ## coefficient matrices of @math{dx/dt = A x + B u} |
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29 ## @item sys |
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30 ## system data structure |
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31 ## @item w |
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32 ## vector of frequencies |
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33 ## @end table |
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34 ## @strong{Output} |
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35 ## @table @var |
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36 ## @item out |
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37 ## frequency response, that is: |
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38 ## @end table |
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39 ## @iftex |
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40 ## @tex |
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41 ## $$ G(j\omega) = (j\omega I-A)^{-1}B $$ |
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42 ## @end tex |
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43 ## @end iftex |
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44 ## @ifinfo |
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45 ## @example |
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46 ## -1 |
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47 ## G(s) = (jw I-A) B |
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48 ## @end example |
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49 ## @end ifinfo |
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50 ## for complex frequencies @math{s = jw}. |
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51 ## @end deftypefn |
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52 |
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53 ## Author: R. Bruce Tenison <btenison@eng.auburn.edu> |
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54 ## Author: David Clem |
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55 ## Author: A. S. Hodel <a.s.hodel@eng.auburn.edu> |
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56 ## Created: July 1995 |
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57 ## updated by John Ingram August 1996 for system format |
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58 |
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59 function out = ltifr (a, b, w) |
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60 |
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61 if ((nargin < 2) || (nargin > 3)) |
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62 error("incorrect number of input arguments"); |
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63 endif |
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64 |
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65 if (nargin == 2) |
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66 sys = a; |
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67 w = b; |
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68 if(!isstruct(sys)) |
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69 error("two arguments: 1st must be a system data structure"); |
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70 endif |
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71 |
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72 if (!isvector(w)) |
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73 error("w must be a vector"); |
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74 endif |
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75 |
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76 [nn,nz,mm,pp] = sysdimensions(sys); |
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77 if(mm != 1) error("sys has %d > 1 inputs",mm); endif |
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78 |
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79 [a,b] = sys2ss(sys); |
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80 |
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81 else |
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82 |
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83 if (columns(a) != rows(b)), |
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84 error("ltifr: A(%dx%d), B(%dx%d) not compatibly dimensioned", ... |
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85 rows(a), columns(a), rows(b), columns(b)); |
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86 endif |
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87 |
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88 if(columns(b) != 1) |
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89 error("ltifr: b(%dx%d) must be a single column vector", ... |
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90 rows(b),columns(b)); |
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91 endif |
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92 |
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93 if (!issquare(a)) |
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94 error("ltifr: A(%dx$d) must be square.",rows(a),columns(a)) |
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95 endif |
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96 |
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97 endif |
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98 |
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99 if (!isvector(w)) |
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100 error("w must be a vector"); |
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101 endif |
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102 |
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103 ey = eye(size(a)); |
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104 lw = length(w); |
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105 out = ones(columns(a),lw); |
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106 |
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107 for ii=1:lw, |
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108 out(:,ii) = (w(ii)*ey-a)\b; |
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109 endfor |
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110 endfunction |
