On Sat, Dec 13, 2008 at 08:59:08AM -0800, Aaron wrote:
>
> Hi all,
>
> First I'd like to give heartfelt thank to the sympy team. It's really
> a good package, and it helps me a lot as I'm working on some
> calculations of dynamic systems.
What special kind of calculations do you do?
> I'm a newbie to sympy. The problem is, I do not know whether it is
> possible to get the derivative with respect to a function, not a
> symbol. The code is like this:
>
> t = Symbol("t")
> f = Function("f")
>
> theta = f(t)
> theta_dot = diff(theta,t,1)
> x = theta*theta_dot
> y = diff(x,theta_dot,1)
>
> Then the output is
> D(f(t)*D(f(t), t), D(f(t), t))
>
> However, my expected output should be "theta" or "f(t)" instead.
>
> Does anyone get an idea about this?
Hm, could you tell us more about your problem? I have been thinking
for a while but I have no idea :-(
By,
Friedrich
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