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## Re: compatability- lsim() suggestions?

**From**: |
A S Hodel |

**Subject**: |
Re: compatability- lsim() suggestions? |

**Date**: |
Sat, 8 Mar 2003 15:35:20 -0600 |

On Saturday, March 8, 2003, at 02:35 PM, Paul Kienzle wrote:
...

According to the matlab manual pages, lsim takes
one or more sys arguments. It makes no mention
of other forms, such as ss or tf. Since it is easy
enough to build a sys from ss or tf, this won't be
too much of an issue. Perhaps older versions of
matlab did not take a sys argument?

`(Factual, but tongue in cheek reply:) A long time ago, in a Matlab far
``away,
`control functions only knew about
num,den
num, den, Ts
zer,pol,k
zer,pol,k,Ts
a,b,c,d,
a,b,c,d,Ts

`so controls functions took 6 input formats that used anywhere from 2 to
``5 arguments,
``and functions had to figure out which of the 6 forms were being used by
``looking at
``the number of arguments and whether or not the last argument was a
``positive scalar
``(sampling time), etc.. Octave's 1st controls toolbox did the same. A
``real pain. Then
``Octave developers - already familiar with C++ - had the bright idea of
``using an Octave
``data structure - a single variable that could easily be parsed to know
``what format was
`used. Thus were born the functions
tf2sys
zp2sys
ss2sys
etc.

`Then a year later MATLAB came out with the tf, ss, zpk functions, etc.,
``using MATLAB's
``new object-oriented programming capabilities and a whole new way for
``Octave and
``MATLAB to be incompatible was born. Pretty clever, eh? Now that
``raises some
``pretty involved (pronounced "labor intensive") issues in how to make
``Octave and
``MATLAB "compatible." Given that only one part of that team (and only
``part of that part) is
``interested in pure MATLAB compatibility, some thought needs to be put
``here - including
`thoughts toward backward compatibility.
"Exciting - isn't it?" Draal, Babylon 5.
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