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+## Copyright (C) 1993, 1994, 1995 John W. Eaton
+##
+## This file is part of Octave.
+##
+## Octave 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 2, or (at your option) any
+## later version.
+##
+## Octave 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 Octave; see the file COPYING.  If not, write to the Free
+## Software Foundation, 59 Temple Place, Suite 330, Boston, MA 02111 USA.
+
+## -*- texinfo -*-
+## @deftypefn {Function File} {} damp(@var{p}@{, @var{tsam}@})
+## Displays eigenvalues, natural frequencies and damping ratios
+## of the eigenvalues of a matrix @var{p} or the @var{A}-matrix of a
+## system @var{p}, respectively.
+## If @var{p} is a system, @var{tsam} must not be specified.
+## If @var{p} is a matrix and @var{tsam} is specified, eigenvalues
+## of @var{p} are assumed to be in @var{z}-domain.
+## @end deftypefn
+## @seealso{eig}
+
+## Author: Kai P. Mueller <mueller@ifr.ing.tu-bs.de>
+## Created: September 29, 1997.
+
+function damp (p, tsam)
+
+  ## assume a continuous system
+  DIGITAL = 0;
+  if(nargin < 1 || nargin > 2)
+    usage("damp(p,[ tsamp])")
+  endif
+  if(is_struct(p))
+    if (nargin != 1)
+      error("damp: when p is a system, tsamp parameter is not allowed.");
+    endif
+    [aa, b, c, d, t_samp] = sys2ss(p);
+    DIGITAL = is_digital(p);
+  else
+    aa = p;
+    if (nargin == 2)
+        DIGITAL = 1;
+        t_samp = tsam;
+    endif
+  endif
+  if (!is_square(aa))
+    error("damp: Matrix p is not square.")
+  endif
+  if (DIGITAL && t_samp <= 0.0)
+    error("damp: Sampling time tsam must not be <= 0.")
+  endif
+
+  ## all checks done.
+  e = eig(aa);
+  [n, m] = size(aa);
+  if (DIGITAL)
+    printf("  (discrete system with sampling time %f)\n", t_samp);
+  endif
+  printf("............... Eigenvalue ...........     Damping     Frequency\n");
+  printf("--------[re]---------[im]--------[abs]----------------------[Hz]\n");
+  for i = 1:n
+    pole = e(i);
+    cpole = pole;
+    if (DIGITAL)
+      cpole = log(pole) / t_samp;
+    endif
+    d0 = -cos(atan2(imag(cpole), real(cpole)));
+    f0 = 0.5 / pi * abs(cpole);
+    if (abs(imag(cpole)) < eps)
+      printf("%12f         ---  %12f  %10f  %12f\n",
+             real(pole), abs(pole), d0, f0);
+    else
+      printf("%12f %12f %12f  %10f  %12f\n",
+             real(pole), imag(pole), abs(pole), d0, f0);
+    endif
+  endfor
+
+endfunction