Janardhanan Sivaramakrishnan

Nice function especially useful for reducing systems coming from matlab linearizations.

There is a little mistake in the code easily catch by M-lint

wrong

if ~isreal(r) || (fix(r)~=r) || (r<1) || (r>n) %%% here n is undefined
    error('Invalid value of reduced model order')
end
[num,den]=tfdata(G,'v');
D_fact=num(1)/den(1);
num=num-D_fact*den;
num1=num(end:-1:1)/den(1);
den1=den(end:-1:1)/den(1);
n=length(den1)-1;

right

[num,den]=tfdata(G,'v');
D_fact=num(1)/den(1);
num=num-D_fact*den;
num1=num(end:-1:1)/den(1);
den1=den(end:-1:1)/den(1);
n=length(den1)-1;

if ~isreal(r) || (fix(r)~=r) || (r<1) || (r>n)
    error('Invalid value of reduced model order')
end

I would like to know if the author agree with this correction.

Apart from this correction the function works nicely. I find it very useful and I thank the author for sharing it.

Regards.

No documentation of the code and error

??? Undefined function or variable "ips".

Error in ==> balancetrunc at 119
   Pb1=P.b(:,1:ips);

for

>> AD

AD =

   -3.2247 -1.7331 -0.6210
    2.0000 0 0
         0 1.0000 0

>> BD

BD =

     1
     0
     0

>> CD

CD =

         0 0 0.5988

>> DD

DD =

     0