On Mon, Apr 6, 2015 at 8:16 AM, Chris Smith <[email protected]> wrote:
> In line 4585 of ode.py RootOf instances return the Rational forms, e.g., > > >>> RootOf(2.3*x-2,0) > 20/23. > Ah. I suppose this will not be so easy to fix, as the float stuff with the polys does not work so well. We should at least not use RootOf unless we have to, though. > > The default behavior of solve is "Float in, Float out" unless > rational=True. (The docstring for solve should be updated to say that the > default behavior is rational=None.) > Good to know. I'm glad this is the behavior now. Aaron Meurer > > On Saturday, April 4, 2015 at 11:27:07 PM UTC-5, G B wrote: >> >> Still wrestling with dsolve... Below is a call with an arbitrary >> differential equation. Any idea why dsolve is returning terms with these >> enormous integers? All of the coefficients are floats in this case. The >> expression is impervious to .n() (as mentioned in my earlier question). >> Converting to a numpy function to evaluate the results works, but throws an >> exception when called. >> >> I can't seem to get past this point in the analysis. Any idea how I can >> get this into a form I can continue working with? >> >> A=symbols(r'A',cls=Function) >> t=symbols(r't') >> Eq4=-123456.78*A(t)-9876.54*A(t).diff(t)-0.00032*A(t).diff( >> t,2)+1357908.64 >> soln=dsolve(Eq4) >> print(soln.n()) >> >> A(t) == C1*exp(125*t*(-33935533038108675 - >> sqrt(1151618536954453541512853661417481))/274877906944) + >> C2*exp(125*t*(-33935533038108675 + >> sqrt(1151618536954453541512853661417481))/274877906944) + 10.999060885923 >> >> >> fn=lambdify(t,soln.rhs,'numpy') >> >> >> fn(3.2) >> >> >> ---------------------------------------------------------------------------AttributeError >> Traceback (most recent call >> last)<ipython-input-42-bde0572cbbe1> in <module>()----> 1 fn(3.2) >> //anaconda/lib/python3.4/site-packages/numpy/__init__.py in >> <lambda>(_Dummy_73) >> AttributeError: 'int' object has no attribute 'sqrt' >> >> -- > You received this message because you are subscribed to the Google Groups > "sympy" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To post to this group, send email to [email protected]. > Visit this group at http://groups.google.com/group/sympy. > To view this discussion on the web visit > https://groups.google.com/d/msgid/sympy/1cbc6317-96c6-45e8-9122-a9e346f38f96%40googlegroups.com > <https://groups.google.com/d/msgid/sympy/1cbc6317-96c6-45e8-9122-a9e346f38f96%40googlegroups.com?utm_medium=email&utm_source=footer> > . > > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "sympy" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/sympy. To view this discussion on the web visit https://groups.google.com/d/msgid/sympy/CAKgW%3D6Jzeqg6uwnw0_dHEQvhbXE5TkoH4j6nhq%3DVjSX-iHzmjQ%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
