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1 ## Copyright (C) 1996, 1998 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{num}, @var{den}] =} zp2tf (@var{zer}, @var{pol}, @var{k}) |
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21 ## Converts zeros / poles to a transfer function. |
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22 ## @strong{Inputs} |
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23 ## @table @var |
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24 ## @item zer |
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25 ## @itemx pol |
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26 ## vectors of (possibly complex) poles and zeros of a transfer |
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27 ## function. Complex values should appear in conjugate pairs |
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28 ## @item k |
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29 ## real scalar (leading coefficient) |
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30 ## @end table |
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31 ## @code{[num,den] = zp2tf(zer,pol,k)} forms the transfer function |
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32 ## @code{num/den} from the vectors of poles and zeros. |
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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 ## (With help from students Ingram, McGowan.) |
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37 |
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38 function [num, den] = zp2tf (zer, pol, k) |
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39 |
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40 ## Find out whether data was entered as a row or a column vector and |
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41 ## convert to a column vector if necessary. |
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42 |
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43 [rp,cp] = size(pol); |
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44 [rz,cz] = size(zer); |
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45 |
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46 if(!(isvector(zer) | isempty(zer)) ) |
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47 error(sprintf("zer(%dx%d) must be a vector",rz,cz)); |
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48 elseif(!(isvector(pol) | isempty(pol)) ) |
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49 error(sprintf("pol(%dx%d) must be a vector",rp,cp)); |
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50 elseif(length(zer) > length(pol)) |
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51 error(sprintf("zer(%dx%d) longer than pol(%dx%d)",rz,cz,rp,cp)); |
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52 endif |
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53 |
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54 ## initialize converted polynomials |
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55 |
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56 num = k; den = 1; |
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57 |
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58 ## call __zp2ssg2__ if there are complex conjugate pairs left, otherwise |
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59 ## construct real zeros one by one. Repeat for poles. |
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60 |
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61 while(!isempty(zer)) |
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62 if( max(abs(imag(zer))) ) [poly, zer] = __zp2ssg2__ (zer); |
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63 else poly = [1, -zer(1)]; |
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64 zer = zer(2:length(zer)); endif |
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65 num = conv(num,poly); |
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66 endwhile |
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67 |
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68 while(!isempty(pol)) |
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69 if( max(abs(imag(pol))) ) [poly, pol] = __zp2ssg2__ (pol); |
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70 else poly = [1, -pol(1)]; |
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71 pol = pol(2:length(pol)); endif |
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72 den = conv(den,poly); |
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73 endwhile |
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74 |
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75 endfunction |
