Hi Friedrich, Sorry for not making it clear.
>What special kind of calculations do you do? Basically differentiation and matrix manipulation >Hm, could you tell us more about your problem? I have been thinking for a while but I have no idea :-( Sorry. Generally speaking, I need to calculate the following t indicates time theta (an angle) is a function of t, but the formula is unknown. so theta = f(t) theta_dot indicates the deviation of theta with respect to t x is a function of both theta and theta_dot now, I need to calculate the partial differentiation (x w.r.t theta_dot) diff(x,theta_dot) Is it clear? Best regards, Aaron ps. I've not tried your method given in your second email yet. Thanks very much for it. I'll respond to it later after some investigation. On Sun, Dec 14, 2008 at 5:19 AM, Friedrich Hagedorn <[email protected]>wrote: > > 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 > > > > > --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "sympy" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/sympy?hl=en -~----------~----~----~----~------~----~------~--~---
