From bug-octave-request at bevo dot che dot wisc dot edu Mon Nov  4 15:59:16 2002
Subject: Re: a bug in syssub.m (was sysmult.m)
From: "John W. Eaton" <jwe at bevo dot che dot wisc dot edu>
To: A S Hodel <a dot s dot hodel at Eng dot Auburn dot EDU>
Cc: "K.Yoshida" <kyoshida at ecs dot shimane-u dot ac dot jp>, bug-octave@bevo.che.wisc.edu
Date: Mon, 4 Nov 2002 15:59:13 -0600

On  2-Nov-2002, A S Hodel <a dot s dot hodel at Eng dot Auburn dot EDU> wrote:

| >
| > I've found a bug in sysmult.m. When the denominators of transfer
| > functions sys1 and sys2 are the same, the function "sysmult(sys1,sys2)"
| > returns the sum of sys1 and sys2.
| > In sysmult.m, in the 9th line below from the line "## perform the 
| > subtract"
| > the line
| > sys = tf2sys(Gnum+Hnum,Gden,GT,Gin,Gout);
| > should be
| > sys = tf2sys(Gnum-Hnum,Gden,GT,Gin,Gout);
| 
| The problem is not in sysmult, but in syssub.  The correction listed 
| above is correct for that subroutine.
| Here's a patch:
| 
| *** /sw/share/octave/2.1.35/m/control/system/syssub.m	Thu Oct 31 
| 18:59:31 2002--- ./syssub.m	Sat Nov  2 15:27:34 2002
| ***************
| *** 81,87 ****
|          [Hnum,Hden,HT,Hin,Hout] = sys2tf(Hsys);
|          if(length(Hden) == length(Gden) )
|            if( (Hden == Gden) & (HT == GT) )
| !           sys = tf2sys(Gnum+Hnum,Gden,GT,Gin,Gout);
|              return
|            endif
|            ## if not, we go on and do the usual thing...
| --- 81,87 ----
|          [Hnum,Hden,HT,Hin,Hout] = sys2tf(Hsys);
|          if(length(Hden) == length(Gden) )
|            if( (Hden == Gden) & (HT == GT) )
| !           sys = tf2sys(Gnum-Hnum,Gden,GT,Gin,Gout);
|              return
|            endif
|            ## if not, we go on and do the usual thing...

I made this change.

Thanks,

jwe



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