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From: "Steve " <steveDEL.bachmeierDEL@yahoo.com>
Newsgroups: comp.soft-sys.matlab
Subject: Re: symbolic partials
Date: Sun, 14 Oct 2007 21:30:31 +0000 (UTC)
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Ahh, yes, you are correct.  However, I was not complete in 
the description of the problem.  What I'm looking for is 
how to take partials with respect to symbols that are 
functions of time.

syms x y
x=sym('x(t)')
y=sym('y(t)')
f=x*y
diff(f,x)=error

I need the symbols to be functions of time so I can 
differentiate, etc. in previous steps.  Is there a way to 
do this without converting all symbols that are functions 
of time back to simply their variables?

Thanks,
Steve


dsv <deflagrator@gmail.com> wrote in message 
<1192227295.371965.273400@q5g2000prf.googlegroups.com>...
> I seem to be able to differentiate perfectly fine. I am 
running Matlab
> 2006Rb.
> 
> syms x y
> f=x*y;
> diff(f,x)
> 
> ans =
> 
> y
> 
> -dsv
> 
> On Oct 12, 4:36 pm, "Steve " 
<steveDEL.bachmeier...@yahoo.com> wrote:
> > Oops, I meant that diff(f,'x') gives me zero.  So,
> >
> > f=x*y
> > diff(f,'x')
> > ans=0
> >
> > I'm looking for
> > ans=y
> >
> > Ideas?
> >
>