Add a useful package (from Source forge) for octave

[CreaPhase.git] / octave_packages / control-2.3.52 / tfpoly2str.m

diff --git a/octave_packages/control-2.3.52/tfpoly2str.m b/octave_packages/control-2.3.52/tfpoly2str.m
new file mode 100644 (file)
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+++ b/octave_packages/control-2.3.52/tfpoly2str.m
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+## Copyright (C) 2012   Lukas F. Reichlin
+##
+## This file is part of LTI Syncope.
+##
+## LTI Syncope is free software: you can redistribute it and/or modify
+## it under the terms of the GNU General Public License as published by
+## the Free Software Foundation, either version 3 of the License, or
+## (at your option) any later version.
+##
+## LTI Syncope is distributed in the hope that it will be useful,
+## but WITHOUT ANY WARRANTY; without even the implied warranty of
+## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+## GNU General Public License for more details.
+##
+## You should have received a copy of the GNU General Public License
+## along with LTI Syncope.  If not, see <http://www.gnu.org/licenses/>.
+
+## -*- texinfo -*-
+## @deftypefn {Function File} {@var{str} =} tfpoly2str (@var{p})
+## @deftypefnx {Function File} {@var{str} =} tfpoly2str (@var{p}, @var{tfvar})
+## Return the string of a polynomial with string @var{tfvar} as variable.
+## @end deftypefn
+
+## Author: Lukas Reichlin <lukas.reichlin@gmail.com>
+## Created: May 2012
+## Version: 0.1
+
+function str = tfpoly2str (p, tfvar = "x")
+
+  ## TODO: simplify this ugly code
+
+  str = "";
+
+  lp = numel (p);
+
+  if (lp > 0)               # first element (lowest order)
+    idx = find (p);         # first non-zero element
+    if (isempty (idx))
+      str = "0";
+      return;
+    else
+      idx = idx(1);
+    endif
+    a = p(idx);
+
+    if (a < 0)
+      cs = "-";
+    else
+      cs = "";
+    endif
+    
+    if (idx == 1)
+      str = [cs, num2str(abs (a), 4)];
+    else
+      if (abs (a) == 1)
+        str = [cs, __variable__(tfvar, idx-1)];
+      else
+        str = [cs, __coefficient__(a), " ", __variable__(tfvar, idx-1)];
+      endif
+    endif
+
+    if (lp > idx)           # remaining elements of higher order
+      for k = idx+1 : lp
+        a = p(k);
+
+        if (a != 0)
+          if (a < 0)
+            cs = " - ";
+          else
+            cs = " + ";
+          endif
+
+          if (abs (a) == 1)
+            str = [str, cs, __variable__(tfvar, k-1)];
+          else
+            str = [str, cs, __coefficient__(a), " ", __variable__(tfvar, k-1)];
+          endif
+        endif
+      endfor
+
+    endif
+  endif
+
+endfunction
+
+
+function str = __coefficient__ (a)
+
+  b = abs (a);  
+
+  if (b == 1)
+    str = "";
+  else
+    str = num2str (b, 4);
+  endif
+
+endfunction
+
+
+function str = __variable__ (tfvar, n)
+
+  str = [tfvar, "^-", num2str(n)];
+
+endfunction