Thanks for your inputs. I changed the definition of the Function (removed the (t)) About the wording. You would like me to use f, or g for the state functions of time. usually, those stand for some degree of freedom (x, y, ... angles...).
but the litterature also use often: q would it be ok for you if I use: q1, q2, ... ? instead of x, y, ... that would make sense to me. On 10 nov, 18:34, "Aaron S. Meurer" <[email protected]> wrote: > Don't use from sympy import * in docstrings. Import each thing that you use > explicitly. > > Also, make the first line separated from the rest by another newline. > Actually, the first line should be a brief description of what the function > does (like "Computes the Euler-Lagrange blah blah blah"), then the stuff you > currently have can go after that. > > You can test if your doctests are correct by running ./bin/doctest > your_file.py, where your_file is wherever this code is (or just ./bin/doctest > will run it on all files in the sympy/ directory). > > Aside from that, I think it would be slightly better if you just did > > x = Function('x') > …diff(x(t), t) > > i.e., don't make x the whole evaluated Function, just the Function object. > Also, is x a common name for x with this? Generally in SymPy, x is a Symbol, > and things like f, g, and h are Functions, so unless it is what everybody > uses, I would use f instead of x. > > Aaron Meurer > > On Nov 10, 2010, at 9:08 AM, Philippe wrote: > > > also, I am not sure that I put > > from sympy import * > > t = Symbol('t') > > at the best place. > > > On 10 nov, 16:56, Philippe <[email protected]> wrote: > >> is this correct ? > >> to be honnest, it's my first docstring ... > > >> On 10 nov, 16:50, Philippe <[email protected]> wrote: > > >>> from sympy import * > > >>> t = Symbol('t') > > >>> def partial_derivative(equa, param): > >>> """param is a variable, must not be named 'param_sub' > >>> >>> from sympy import * > >>> >>> t = Symbol('t') > >>> >>> k = Symbol('k') > >>> >>> x = Function('x')(t) > >>> >>> partial_derivative(k*diff(x, t)**2 + k * x, x) > >>> k > >>> >>> partial_derivative(k*diff(x, t)**2 + k * x, diff(x, t)) > >>> 2*k*D(x(t), t)""" > > >>> param_sub = Symbol('param_sub') > >>> equa_subs1 = equa.subs(param, param_sub) > >>> dequa_param_sub = diff(equa_subs1, param_sub) > >>> dequa_param = dequa_param_sub.subs(param_sub, param) > >>> return dequa_param > > >>> def lagrange(equa, param): > >>> """param is a list of Function of time > >>> must not use the name 'param_sub' in the equation > >>> >>> from sympy import * > >>> >>> t = Symbol('t') > >>> >>> k = Symbol('k') > >>> >>> x = Function('x')(t) > >>> >>> y = Function('y')(t) > >>> >>> equa = diff(x, t)**2+diff(y, t)**2 + 5 * x > >>> >>> dT_dqvt, dT_dq = lagrange(equa, [x, y]) > >>> >>> print dT_dqvt > >>> [2*D(x(t), t, t), 2*D(y(t), t, t)] > >>> >>> print dT_dq > >>> [5, 0] > >>> >>> equa = k*diff(x, t)**2 + k * x > >>> >>> dT_dqvt, dT_dq = lagrange(equa, [x]) > >>> >>> print dT_dqvt > >>> [2*k*D(x(t), t, t)] > >>> >>> print dT_dq > >>> [k]""" > > >>> vel_var = [diff(e, t) for e in param] > >>> dT_dqv = [partial_derivative(equa, p) for p in vel_var] > >>> dT_dq = [partial_derivative(equa, p) for p in param] > > >>> dT_dqvt = [diff(e, t) for e in dT_dqv] > > >>> return dT_dqvt, dT_dq > > >>> if __name__ == "__main__": > >>> import doctest > >>> doctest.testmod() > > >>> On 10 nov, 15:15, Andy Ray Terrel <[email protected]> wrote: > > >>>> I think this would be a great contribution to the SymPy physics > >>>> module. Can you put some usage doc strings? Then, we can put it in > >>>> the appropriate places. > > >>>> -- Andy > > >>>> On Wed, Nov 10, 2010 at 3:10 AM, Philippe <[email protected]> > >>>> wrote: > >>>>> some usage if needed.. > >>>>> this is my unittest file. > >>>>> the lagrange and partial_derivative functions are in meca.py > > >>>>> - - - - - - - - - - - - > > >>>>> import unittest > >>>>> from sympy import * > >>>>> import meca > > >>>>> class MyTest(unittest.TestCase): > > >>>>> def test_lagrange_1(self): > >>>>> t = Symbol('t') > >>>>> x = Function('x')(t) > >>>>> y = Function('y')(t) > >>>>> dT_dqvt, dT_dq = meca.lagrange(diff(x, t)**2+diff(y, t)**2 + 5 > >>>>> * x, [x, y]) > > >>>>> dT_dqvt_0 = 2*diff(x, t, t) > >>>>> dT_dqvt_1 = 2*diff(y, t, t) > > >>>>> self.assertEquals(dT_dqvt, [dT_dqvt_0, dT_dqvt_1]) > >>>>> self.assertEquals(dT_dq, [5, 0]) > > >>>>> def test_lagrange_2(self): > >>>>> t = Symbol('t') > >>>>> k = Symbol('k') > >>>>> x = Function('x')(t) > >>>>> dT_dqvt, dT_dq = meca.lagrange(k*diff(x, t)**2 + k * x, [x]) > > >>>>> dT_dqvt_0 = 2*k*diff(x, t, t) > > >>>>> self.assertEquals(dT_dqvt, [dT_dqvt_0]) > >>>>> self.assertEquals(dT_dq, [k]) > > >>>>> def test_partial_derivative_1(self): > >>>>> t = Symbol('t') > >>>>> k = Symbol('k') > >>>>> x = Function('x')(t) > >>>>> dE_q = meca.partial_derivative(k*diff(x, t)**2 + k * x, x) > >>>>> dE_q_sol = k > >>>>> self.assertEquals(dE_q, dE_q_sol) > > >>>>> def test_partial_derivative_2(self): > >>>>> t = Symbol('t') > >>>>> k = Symbol('k') > >>>>> x = Function('x')(t) > >>>>> dE_q = meca.partial_derivative(k*diff(x, t)**2 + k * x, > >>>>> diff(x, t)) > >>>>> dE_q_sol = 2*k*diff(x, t) > >>>>> self.assertEquals(dE_q, dE_q_sol) > > >>>>> if __name__ == '__main__': > >>>>> unittest.main() > > >>>>> - - - - - - - - - - - - > > >>>>> On 9 nov, 17:18, Philippe <[email protected]> wrote: > >>>>>> from sympy import * > > >>>>>> t = Symbol('t') > >>>>>> x = Function('x')(t) > >>>>>> y = Function('y')(t) > > >>>>>> def partial_derivative(equa, param): > >>>>>> param_sub = Symbol('param_sub') > >>>>>> equa_subs1 = equa.subs(param, param_sub) > >>>>>> dequa_param_sub = diff(equa_subs1, param_sub) > >>>>>> dequa_param = dequa_param_sub.subs(param_sub, param) > >>>>>> return dequa_param > > >>>>>> def lagrange(equa, param): > >>>>>> """ > >>>>>> param is a list of Function of time > >>>>>> must not use 'q1', 'q2', .... 'qv1', ... in the equation > >>>>>> """ > >>>>>> vel_var = [diff(e, t) for e in param] > >>>>>> dT_dqv = [partial_derivative(equa, p) for p in vel_var] > >>>>>> dT_dq = [partial_derivative(equa, p) for p in param] > > >>>>>> dT_dqvt = [diff(e, t) for e in dT_dqv] > > >>>>>> return dT_dqvt, dT_dq > > >>>>>> On 31 oct, 20:51, Tim Lahey <[email protected]> wrote: > > >>>>>>> On Sun, Oct 31, 2010 at 3:41 PM, Aaron S. Meurer <[email protected]> > >>>>>>> wrote: > > >>>>>>>> I am still trying to fully understand the code below, but if one of > >>>>>>>> the subs is trying to do something like diff(f(x), x).subs(x, g(x)), > >>>>>>>> then you will get an error in SymPy for the above reason. > > >>>>>>>> Aaron Meurer > > >>>>>>> The basic approach is to substitute a symbol for f(x) say f1 and then > >>>>>>> take the derivative > >>>>>>> with respect to that. You know the substitution, so you can reverse > >>>>>>> it. Once the derivative > >>>>>>> is done, you reverse the substitution. Then, you can take the > >>>>>>> derivative with respect to > >>>>>>> x. > > >>>>>>> So, the steps become. > > >>>>>>> 1. Build list of symbols for functions. > >>>>>>> 2. Build a list of substitutions for the functions and the reverse. > >>>>>>> 3. Substitute for the functions. > >>>>>>> 4. Run derivatives with respect to the symbols. > >>>>>>> 5. Substitute functions for the symbols. > >>>>>>> 6. Take any derivatives with respect to the function variables. > > >>>>>>> Hope that helps the explanation. A lot of what's done in the code is > >>>>>>> using > >>>>>>> zip and map to make the code fast, but I originally wrote it as > >>>>>>> above. Python > >>>>>>> has appropriate functions that this should still be fast. > > >>>>>>> Cheers, > > >>>>>>> Tim. > > >>>>>>> -- > >>>>>>> Tim Lahey > >>>>>>> PhD Candidate, Systems Design Engineering > >>>>>>> University of Waterloohttp://www.linkedin.com/in/timlahey > > >>>>> -- > >>>>> 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 > >>>>> athttp://groups.google.com/group/sympy?hl=en. > > > -- > > 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 > > athttp://groups.google.com/group/sympy?hl=en. > > -- 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.
