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1 # Copyright (C) 1996,1998 A. Scottedward Hodel |
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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, 675 Mass Ave, Cambridge, MA 02139, USA. |
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18 |
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19 function outsys = tf2sys(num,den,tsam,inname,outname) |
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20 # |
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21 # sys = tf2sys(num,den{,tsam,inname,outname}) |
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22 # build system data structure from transfer function format data |
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23 # inputs: |
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24 # num, den: coefficients of numerator/denominator polynomials |
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25 # tsam: sampling interval. default: 0 (continuous time) |
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26 # inname, outname: input/output signal names (string variables) |
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27 # outputs: sys = system data structure |
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28 |
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29 # Written by R. Bruce Tenison July 29, 1994 |
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30 # Name changed to TF2SYS July 1995 |
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31 # updated for new system data structure format July 1996 |
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32 # $Revision: 2.0.0.0 $ |
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33 |
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34 save_val = implicit_str_to_num_ok; |
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35 implicit_str_to_num_ok = 1; |
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36 |
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37 # Test for the correct number of input arguments |
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38 if ((nargin < 2) || (nargin > 5)) |
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39 usage('outsys=tf2sys(num,den[,tsam,inname,outname])'); |
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40 return |
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41 endif |
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42 |
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43 # check input format |
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44 if( ! ( (is_vector(num) || is_scalar(num)) && ... |
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45 (is_vector(den) || is_scalar(den))) ) |
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46 error(['num (',num2str(rows(num)),'x',num2str(columns(num)), ... |
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47 ') and den (',num2str(rows(den)),'x',num2str(columns(den)), ... |
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48 ') must be vectors']) |
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49 endif |
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50 |
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51 # strip leading zero coefficients |
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52 num = tf2sysl(num); |
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53 den = tf2sysl(den); |
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54 |
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55 if (length(num) > length(den)) |
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56 error("# of poles (%d) < # of zeros (%d)",length(den)-1, length(num)-1); |
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57 endif |
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58 |
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59 # check sampling interval (if any) |
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60 if(nargin <= 2) tsam = 0; # default |
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61 elseif (isempty(tsam)) tsam = 0; endif |
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62 if ( (! (is_scalar(tsam) && (imag(tsam) == 0) )) || (tsam < 0) ) |
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63 error('tsam must be a positive real scalar') |
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64 endif |
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65 |
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66 outsys.num = num; |
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67 outsys.den = den; |
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68 |
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69 # Set the system vector: active = 0(tf), updated = [1 0 0]; |
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70 outsys.sys = [0 1 0 0]; |
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71 |
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72 # Set defaults |
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73 outsys.tsam = tsam; |
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74 outsys.n = length(den)-1; |
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75 outsys.nz = 0; |
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76 outsys.yd = 0; # assume discrete-time |
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77 # check discrete time |
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78 if(tsam > 0) |
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79 [outsys.n,outsys.nz] = swap(outsys.n, outsys.nz); |
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80 outsys.yd = 1; |
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81 endif |
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82 |
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83 outsys.inname = sysdefioname(1,"u"); |
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84 outsys.outname = sysdefioname(1,"y"); |
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85 outsys.stname = sysdefstname(outsys.n,outsys.nz); |
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86 |
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87 # Set name of input |
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88 if (nargin > 3) |
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89 # make sure its a list of a single string |
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90 if(!isempty(inname)) |
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91 if(!is_list(inname)) inname = list(inname); endif |
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92 if( !is_signal_list(inname) ) |
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93 error("inname must be a string or list of strings"); |
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94 endif |
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95 if(length(inname) > 1) |
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96 warning("tf2sys: %d input names provided; first used",length(inname)); |
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97 inname = inname(1); |
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98 endif |
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99 outsys = syssetsignals(outsys,"in",inname); |
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100 endif |
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101 endif |
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102 |
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103 # Set name of output |
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104 if (nargin > 4) |
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105 if(!isempty(outname)) |
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106 if(!is_list(outname)) outname = list(outname); endif |
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107 if(!is_signal_list(outname)) |
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108 error("outname must be a string or a list of strings"); |
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109 endif |
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110 if(length(outname) > 1) |
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111 warning("tf2sys: %d output names provided; first used",length(outname)); |
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112 outname = outname(1); |
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113 endif |
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114 outsys = syssetsignals(outsys,"out",outname); |
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115 endif |
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116 endif |
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117 |
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118 implicit_str_to_num_ok = save_val; |
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119 endfunction |
