--- a/scripts/control/base/__bodquist__.m
+++ b/scripts/control/base/__bodquist__.m
@@ -17,7 +17,7 @@
 ## Software Foundation, 59 Temple Place, Suite 330, Boston, MA 02111 USA.
 
 ## -*- texinfo -*-
-## @deftypefn {Function File} {[@var{f}, @var{w}] =} __bodquist__ (@var{sys}, @var{w}, @var{out_idx}, @var{in_idx})
+## @deftypefn {Function File} {[@var{f}, @var{w}, @var{rsys} =} __bodquist__ (@var{sys}, @var{w}, @var{out_idx}, @var{in_idx})
 ## used internally by bode, nyquist; compute system frequency response.
 ##
 ## @strong{Inputs}
@@ -27,11 +27,11 @@
 ## @item w
 ## range of frequencies; empty if user wants default
 ## @item out_idx
-## list of outputs; empty if user wants all
+## vector output indices or list of output signal names; empty if user wants all
 ## @item in_idx
-## list of inputs; empty if user wants all
+## vector of input indices of list of input signal names; empty if user wants all
 ## @item rname
-## name of routine that called __bodquist__ ("bode" or "nyquist")
+## name of routine that called __bodquist__ ("bode", "nyquist", or "nichols")
 ## @end table
 ## @strong{Outputs}
 ## @table @var
@@ -39,18 +39,19 @@
 ## list of frequencies
 ## @item f
 ## frequency response of sys; @math{f(ii) = f(omega(ii))}
+## @item rsys
+## system with selected inputs and outputs
 ## @end table
-## @strong{Note} __bodquist__ could easily be incorporated into a Nichols
-## plot function; this is in a "to do" list.
 ##
-## Both bode and nyquist share the same introduction, so the common parts are
+## @code{bode}, @code{nichols}, and @code{nyquist} share the same 
+## introduction, so the common parts are
 ## in __bodquist__.  It contains the part that finds the number of arguments,
 ## determines whether or not the system is SISO, and computes the frequency
 ## response.  Only the way the response is plotted is different between the
-## two functions.
+## these functions.
 ## @end deftypefn
 
-function [f, w] = __bodquist__ (sys, w, outputs, inputs, rname)
+function [f, w, rsys] = __bodquist__ (sys, w, outputs, inputs, rname)
 
   ## check number of input arguments given
   if (nargin != 5)
@@ -73,7 +74,12 @@
     if (isempty(inputs))
       inputs = 1:mm;                    # use all inputs
       warning([rname,": outputs specified but not inputs"]);
+    elseif(is_signal_list(inputs) | isstr(inputs))
+      inputs = sysidx(sys,"in",inputs);
     endif
+    if(is_signal_list(outputs) | isstr(outputs))
+      outputs = sysidx(sys,"out",outputs);
+    end
     sys = sysprune(sys,outputs,inputs);
     [nn,nz,mm,pp ] = sysdimensions(sys);
   endif
@@ -154,4 +160,7 @@
   w = w(w_idx);
   f = f(w_idx);
 
+  ## set rsys to pruned system
+  rsys = sys;
+
 endfunction

--- a/scripts/control/base/bode.m
+++ b/scripts/control/base/bode.m
@@ -1,4 +1,4 @@
-## Copyright (C) 1996, 1998 Auburn University.  All rights reserved.
+## Copyright (C) 1996, 1998, 2000 Auburn University.  All rights reserved.
 ##
 ## This file is part of Octave.
 ##
@@ -61,8 +61,13 @@
 ## @end enumerate
 ## @item out_idx
 ## @itemx in_idx
-## the indices of the output(s) and input(s) to be used in
-## the frequency response; see @code{sysprune}.
+##
+## The names or indices of outputs and inputs to be used in the frequency
+## response.  See @code{sysprune}.
+##
+## @example
+## bode(sys,[],"y_3",list("u_1","u_4");
+## @end example
 ## @end table
 ## @strong{Outputs}
 ## @table @var
@@ -126,7 +131,7 @@
     error ("bode: invalid value of plot_style specified");
   endif
 
-  [f, w] = __bodquist__ (sys, w, outputs, inputs, "bode");
+  [f, w, sys] = __bodquist__ (sys, w, outputs, inputs, "bode");
 
   [stname,inname,outname] = sysgetsignals(sys);
   systsam = sysgettsam(sys);

--- a/scripts/control/base/nichols.m
+++ b/scripts/control/base/nichols.m
@@ -37,8 +37,8 @@
 ##          (3) A "smoothing" routine is used to ensure that the plot phase does
 ##              not change excessively from point to point and that singular
 ##              points (e.g., crossovers from +/- 180) are accurately shown.
-##   outputs, inputs: the indices of the output(s) and input(s) to be used in
-##     the frequency response; see sysprune.
+##   outputs, inputs: the names or indices of the output(s) and input(s) 
+##     to be used in the frequency response; see sysprune.
 ## outputs:
 ##    mag, phase: the magnitude and phase of the frequency response
 ##       G(jw) or G(exp(jwT)) at the selected frequency values.
@@ -67,7 +67,7 @@
     inputs = [];
   endif
 
-  [f, w] = __bodquist__ (sys, w, outputs, inputs, "nichols");
+  [f, w, sys] = __bodquist__ (sys, w, outputs, inputs, "nichols");
 
   [stname,inname,outname] = sysgetsignals(sys);
   systsam = sysgettsam(sys);

--- a/scripts/control/base/nyquist.m
+++ b/scripts/control/base/nyquist.m
@@ -119,7 +119,7 @@
 
   ## signal to __bodquist__ who's calling
 
-  [f, w] = __bodquist__ (sys, w, outputs, inputs, "nyquist");
+  [f, w, sys] = __bodquist__ (sys, w, outputs, inputs, "nyquist");
 
   ## Get the real and imaginary part of f.
   realp = real(f);

--- a/scripts/control/system/sysprune.m
+++ b/scripts/control/system/sysprune.m
@@ -1,4 +1,4 @@
-## Copyright (C) 1996, 1998 Auburn University.  All rights reserved.
+## Copyright (C) 1996, 1998, 2000 Auburn University.  All rights reserved.
 ##
 ## This file is part of Octave.
 ##
@@ -26,9 +26,16 @@
 ## system data structure
 ## @item out_idx
 ## @itemx in_idx
-## list of connections indices; the new
-## system has outputs y(out_idx(ii)) and inputs u(in_idx(ii)).
+##
+## Indices or signal names of the outputs and inputs to be kept in the returned
+## system; remaining connections are "pruned" off.
 ## May select as [] (empty matrix) to specify all outputs/inputs.
+##
+## @example
+## retsys = sysprune(Asys,[1:3,4],"u_1");
+## retsys = sysprune(Asys,list("tx","ty","tz"), 4);
+## @end example
+##
 ## @end table
 ##
 ## @strong{Outputs}
@@ -62,6 +69,14 @@
   if(isempty(input_idx)) input_idx = 1:mm; endif
   if(isempty(state_idx)) state_idx = 1:(nn+nz); endif
 
+  ## check for signal names
+  if(is_signal_list(output_idx) | isstr(output_idx))
+    output_idx = sysidx(sys,"out",output_idx);
+  endif
+  if(is_signal_list(input_idx) | isstr(input_idx))
+    input_idx = sysidx(sys,"in",input_idx);
+  endif
+
   ## check dimensions
   if( !(is_vector(output_idx) | isempty(output_idx) )  )
     if(!is_matrix(output_idx))