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Re: Laplace transform

From: A. Scottedward Hodel
Subject: Re: Laplace transform
Date: Mon, 19 Jul 1999 21:32:39 -0500

If you're working with linear, time-invariant systems,
LaPlace transforms (of sorts) can be taken with
the controls toolbox by converting a single-input, single-output
state space system to poles and zeros; 
    [zer,pol,kk] = sys2zp(ss2sys(a,b,c,d))
or just
    [zer,pol,kk] = ss2zp(a,b,c,d)

That's not quite the 
same thing as taking the LaPlace transform of a signal
x(t), which requires evaluation of the (one-sided transform) integral

\int_0^\infty x(t) e^{-st} dt

[might have the sign in the exponent reversed; I'm hacking this 
out by memory]

A S Hodel Assoc. Prof. Dept Elect Eng, Auburn Univ,AL  36849-5201
On leave at NASA Marshall Space Flight Center (256) 544-1426
Address until 15 Mar 2000:Mail Code TD-55, MSFC, Alabama, 35812

>From: Daniel Tourde <address@hidden>
>To: "A. Scottedward Hodel" <address@hidden>
>Subject: Re: Laplace transform
>Date: Tue, Jul 20, 1999, 8:11 AM

>"A. Scottedward Hodel" wrote:
>> I've usually seen the LaPlace transform as a symbolic manipulation;
>> Octave doesn't have that yet.
>> There is the FFT function for the Fourier transform (equivalent to
>> Laplace on the imaginary axis).  There is also the polyval
>> function which can be used to evaluate LaPlace transforms.
>OK. Thanks for your answer
>  Daniel
>Daniel TOURDE                                   E-mail : address@hidden
>The Aeronautical Research Institute of Sweden   Tel : +46 8 55 54 93 44
>P.O. Box 11021 S-161 11 BROMMA, Sweden          Fax : +46 8    25 34 81

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