ADDED   mttroot/mtt/bin/trans/m/mtt_sfreq.m
Index: mttroot/mtt/bin/trans/m/mtt_sfreq.m
==================================================================
--- /dev/null
+++ mttroot/mtt/bin/trans/m/mtt_sfreq.m
@@ -0,0 +1,51 @@
+function [w,y,y_theta] = mtt_sfreq(system_name,theta,indices);
+  ## usage: [t,y,y_theta] = mtt_sfreq(system_name,theta);
+  ##
+  ## Frequency response with name system_name and parameter vector theta
+  ## The order of components in theta is determined in system_numpar.txt:
+  ## y_theta contains the corresponding sensitivity functions
+  ## Assumes system generated by the sBG approach
+  ## Copyright (C) 1999 by Peter J. Gawthrop
+
+  ## 	$Id$	
+
+  ## Assumes SISO system 
+
+  global mtt_n_parameters mtt_parameters # Global "argc argv"
+
+  if nargin<3
+    indices = ones(size(theta));
+  endif
+  
+  N = length(theta);
+  if N!=length(indices)
+    error(sprintf("The length (%i) of indices must be the same as that of theta (%i)",length(indices),N));
+  endif
+  
+
+  eval(sprintf("%s_simpar;", system_name)); # Read the "simulation" parameters
+  w = logspace(mttwmin,mttwmax,mttwsteps)'; # Frequency range
+  
+  y_theta = [];
+  mtt_n_parameters = 2*N;
+  mtt_parameters(2:2:2*N) = theta; # The actual parameters
+  for i = 1:N
+    if indices(i)
+      mtt_parameters(1:2:2*N-1) = 0; # The sensitivity switches are off
+      mtt_parameters(2*i-1) = 1;	# Set the approriate sensitivity switch
+				# on
+      eval(sprintf("%s_numpar;", system_name)); # Read the parameters
+      eval(sprintf("[A,B,C,D,E] = %s_dm;", system_name)); # Evaluate the descriptor matrices
+      fr = dm2fr(A,B,C,D,E,w);
+      y_theta = [y_theta fr(:,2)]; # Sensitivity frequency response
+    endif
+    
+  endfor
+
+  y = fr(:,1);			# Actual frequency response
+  
+  
+endfunction
+
+
+