Re: Inverse Laplace transform?

[A S Hodel]

If you have the coefficients (numerical) of a rational function  
(poles/zeros, etc.) you can use the controls toolbox (ss, zp, tf) to  
convert from a state space form to transfer function.  Alternatively,  
you can use the impulse function to get the time-domain function  
corresponding to a strictly proper Laplace domain transfer function.


On Dec 10, 2006, at 2:25 PM, Joe Koski wrote:

> on 12/10/06 12:31 PM, Doug Stewart at address@hidden wrote:
>
> > Joe Koski wrote:
> > > on 12/10/06 10:36 AM, Doug Stewart at address@hidden wrote:
> > >
> > >
> > > > Is there an inverse Laplace transform function in Octave?
> > > > Doug Stewart
> > >
> > > Doug,
> > >
> > > Check ifft at http://octave.sourceforge.net/index/index.html, or  
> > > help ifft
> > > at the octave prompt.
> > >
> > > Joe
> > Thanks Joe
> > I did look there and there is nothing for Inverse Laplace  
> > transform that
> > I can see.
> >
> >
> > I have written up a crude version that is not ready for prime time  
> > yet.
> > I thought I would ask before I spent the time to reinvent the  
> > wheel :-)
> >
> > What I have is a function ( for the controls tool box) that takes  
> > in a
> > sys type transfer function.
> > It then uses the residue function to do the partial fraction
> > expansion.From this I form up a string  that is the time  
> > representation
> > of each factor.  What I am having a little difficulty with is how to
> > get  the string formatted nicely.
> >
> > I have a cell array with each location holding a string that is  
> > the time
> > representation of a term.
> > What I want to do  is take  these and form them into one long string
> > that has all the "+"'s and "-"'s between each term properly formated.
> >
> > So any help would be appreciated.
> >
> > resultstring = cell(1,1)  "+" cell(2,1) "-" cell(3,1)
> >
> > is what I can't seem to do?
> >
> > Thanks in advance for any help.
> >
> > Doug Stewart
>
> Doug,
>
> Sorry, I was reading Fourier instead of Laplace transform. I guess  
> I was
> just seeing the word transform. For calculation of inverse Laplace
> transforms, I use Maxima, a symbolic math package, and it works well.
>
> Sorry for the confusion.
>
> Joe
>
>
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