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1 ## Copyright (C) 1996, 1999 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} {@var{retval} =} is_digital (@var{sys}) |
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21 ## Return nonzero if system is digital; |
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22 ## inputs: |
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23 ## sys: system data structure |
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24 ## eflg: 0 [default] exit with an error if system is mixed (continuous and |
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25 ## discrete components) |
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26 ## : 1 print a warning if system is mixed (continuous and discrete) |
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27 ## : 2 silent operation |
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28 ## outputs: |
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29 ## DIGITAL: 0: system is purely continuous |
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30 ## : 1: system is purely discrete |
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31 ## : -1: system is mixed continuous and discrete |
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32 ## Exits with an error of sys is a mixed (continuous and discrete) system |
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33 ## @end deftypefn |
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34 |
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35 ## Author: A. S. Hodel <a.s.hodel@eng.auburn.edu> |
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36 ## Created: July 1996 |
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37 |
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38 function DIGITAL = is_digital (sys, eflg) |
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39 |
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40 switch(nargin) |
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41 case(1), eflg = 0; |
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42 case(2), |
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43 if( isempty(find(eflg == [0, 1, 2])) ) |
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44 error("invalid value of eflg=%d (%e)",eflg,eflg); |
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45 endif |
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46 otherwise, |
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47 usage("DIGITAL = is_digital(sys{,eflg})"); |
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48 endswitch |
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49 |
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50 ## checked for sampled data system (mixed) |
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51 ## discrete system |
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52 sysyd = sysgetsignals(sys,"yd"); |
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53 [nn,nz] = sysdimensions(sys); |
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54 cont = sum(sysyd == 0) + nn; |
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55 tsam = sysgettsam(sys); |
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56 dig = sum(sysyd != 0) + nz + tsam; |
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57 |
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58 ## check for mixed system |
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59 if( cont*dig != 0) |
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60 switch(eflg) |
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61 case(0), |
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62 error("continuous/discrete system; use syscont, sysdisc, or c2d first"); |
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63 case(1), |
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64 warning("is_digital: mixed continuous/discrete system"); |
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65 endswitch |
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66 dig_sign = -1; |
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67 else |
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68 dig_sign = 1; |
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69 endif |
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70 |
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71 DIGITAL = dig_sign*(tsam > 0); |
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72 |
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73 endfunction |
