--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/m-toolbox/classes/+utils/@math/getdc.m	Wed Nov 23 19:22:13 2011 +0100
@@ -0,0 +1,58 @@
+% GETDC get the DC gain factor for a pole-zero model
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%
+% DESCRIPTION
+% 
+% A zpk model in matlab notation is an object of the type:
+% 
+%         (s-z1)...(s-zN)
+% zpk = k*----------------
+%         (s-p1)...(s-pn)
+% 
+% the zero-frequency-gain (zfg) or DC gain of this object is obtained by
+% the equation, for s = 0.
+% LTPDA pzmodels are constructed by poles, zeros and DC gain. This means
+% that the value stored in the 'gain' field of the model is the dc gain!
+% This function calculate k.
+% 
+% CALL:
+% 
+%     dc = getdc(z,p,k)
+% 
+% INPUT:
+% 
+%     z: zeros
+%     p: poles
+%     k: gain coefficient
+%       
+% 
+% OUTPUT:
+% 
+%     dc: dc gain of the model 
+% 
+% NOTE:
+% 
+%     
+% 
+%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+% VERSION: $Id: getdc.m,v 1.2 2010/02/22 15:14:17 luigi Exp $
+%
+% HISTORY:     08-10-2008 L Ferraioli
+%                 Creation
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+function dc = getdc(z,p,k)
+
+zrs = prod(-1*z);
+pls = prod(-1*p);
+
+dc = k*zrs/pls;
+
+end
+
+
+
+
+
+
+