I don't. 0 sounds unlikely but may be correct given the maths. Just realised that again the error reported wasn't produced by the posted code. I get the error shown in my previous post when I try to evaluate the integral using a value for n other than 1 or 2 e.g. 1.1. Given that my ultimate aim is to explore the influence of this n parameter on the shown integral, do you think that the reported error indicates that I should be looking to rework my formulations or is it simply indicative of a software bug?
Regards, Will On Wednesday, May 29, 2013 4:10:12 AM UTC+1, Aaron Meurer wrote: > > Do you know what the right answer should be? It gives 0 in Mateusz's > new-polys branch. > > Aaron Meurer > > On Tue, May 28, 2013 at 11:30 AM, Will Furnass > <[email protected] <javascript:>> wrote: > > Thanks Aaron. My code now looks as follows (T is now a lambda function > and > > the integral is evaluated over t=0..oo): > > > > ... > > T = lambda t: Piecewise((0, t < 0), (k * D * pi * dx * expr8 / Q, t >= > 0)) > > > > curve_expr = integrate(T(t - (x/V)), (x, 0, L)) > > vals = { > > P : 0.00022, > > k : 0.5, > > tau_s : 0.01, > > tau_a : 2.0, > > Q : 0.01, > > D : 0.125, > > L : 1225, > > n : 2, > > dx : 1} > > Integral(curve_expr, (t, 0, oo)).subs(vals).doit() > > > > I now get the following error, regardless of whether I use the git > master or > > mattpap's new-polys branch: > > > > AttributeError Traceback (most recent call > last) > > <ipython-input-7-55341b44f4e2> in <module>() > > 1 #plot(turb_curve_expr.subs(vals), (t, 0, 3600)) > > ----> 2 Integral(turb_curve_expr, (t, 0, oo)).subs(vals).doit() > > > > /usr/local/lib/python2.7/dist-packages/sympy/integrals/integrals.pyc in > > doit(self, **hints) > > 886 antideriv = None > > 887 else: > > --> 888 antideriv = self._eval_integral(function, > xab[0], > > meijerg=meijerg1, risch=risch, conds=conds) > > 889 if antideriv is None and meijerg1 is True: > > 890 ret = try_meijerg(function, xab) > > > > /usr/local/lib/python2.7/dist-packages/sympy/integrals/integrals.pyc in > > _eval_integral(self, f, x, meijerg, risch, conds) > > 1113 # Piecewise antiderivatives need to call special > integrate. > > 1114 if f.func is Piecewise: > > -> 1115 return f._eval_integral(x) > > 1116 > > 1117 # let's cut it short if `f` does not depend on `x` > > > > > /usr/local/lib/python2.7/dist-packages/sympy/functions/elementary/piecewise.pyc > > > > in _eval_integral(self, x) > > 197 def _eval_integral(self, x): > > 198 from sympy.integrals import integrate > > --> 199 return Piecewise(*[(integrate(e, x), c) for e, c in > > self.args]) > > 200 > > 201 def _eval_interval(self, sym, a, b): > > > > /usr/local/lib/python2.7/dist-packages/sympy/utilities/decorator.pyc in > > threaded_func(expr, *args, **kwargs) > > 31 func(expr.rhs, *args, > > **kwargs)) > > 32 else: > > ---> 33 return func(expr, *args, **kwargs) > > 34 > > 35 return threaded_func > > > > /usr/local/lib/python2.7/dist-packages/sympy/integrals/integrals.pyc in > > integrate(*args, **kwargs) > > 1587 > > 1588 if isinstance(integral, Integral): > > -> 1589 return integral.doit(deep=False, meijerg=meijerg, > > conds=conds, risch=risch) > > 1590 else: > > 1591 return integral > > > > /usr/local/lib/python2.7/dist-packages/sympy/integrals/integrals.pyc in > > doit(self, **hints) > > 886 antideriv = None > > 887 else: > > --> 888 antideriv = self._eval_integral(function, > xab[0], > > meijerg=meijerg1, risch=risch, conds=conds) > > 889 if antideriv is None and meijerg1 is True: > > 890 ret = try_meijerg(function, xab) > > > > /usr/local/lib/python2.7/dist-packages/sympy/integrals/integrals.pyc in > > _eval_integral(self, f, x, meijerg, risch, conds) > > 1235 try: > > 1236 if conds == 'piecewise': > > -> 1237 h = heurisch_wrapper(g, x, hints=[]) > > 1238 else: > > 1239 h = heurisch(g, x, hints=[]) > > > > /usr/local/lib/python2.7/dist-packages/sympy/integrals/heurisch.pyc in > > heurisch_wrapper(f, x, rewrite, hints, mappings, retries, degree_offset, > > unnecessary_permutations) > > 124 > > 125 res = heurisch(f, x, rewrite, hints, mappings, retries, > > degree_offset, > > --> 126 unnecessary_permutations) > > 127 if not isinstance(res, Basic): > > 128 return res > > > > /usr/local/lib/python2.7/dist-packages/sympy/integrals/heurisch.pyc in > > heurisch(f, x, rewrite, hints, mappings, retries, degree_offset, > > unnecessary_permutations) > > 422 > > 423 u_split = _splitter(denom) > > --> 424 v_split = _splitter(Q) > > 425 > > 426 polys = list(v_split) + [ u_split[0] ] + special.keys() > > > > /usr/local/lib/python2.7/dist-packages/sympy/integrals/heurisch.pyc in > > _splitter(p) > > 399 return (c_split[0], q * c_split[1]) > > 400 > > --> 401 q_split = _splitter(cancel(q / s)) > > 402 > > 403 return (c_split[0]*q_split[0]*s, > > c_split[1]*q_split[1]) > > > > /usr/local/lib/python2.7/dist-packages/sympy/integrals/heurisch.pyc in > > _splitter(p) > > 387 > > 388 if _derivation(y) is not S.Zero: > > --> 389 c, q = p.as_poly(y).primitive() > > 390 > > 391 q = q.as_expr() > > > > AttributeError: 'NoneType' object has no attribute 'primitive' > > > > > > Regards, > > > > Will > > > > > > On Tuesday, 28 May 2013 15:43:44 UTC+1, Aaron Meurer wrote: > >> > >> Are you sure you're using the git head? The T(t - (x/V)) in the > >> integral is not allowed (we stopped making SymPy objects arbitrarily > >> callable). I'm not sure if you meant for that to be a substitution or > >> a multiplication, so I didn't try it further. Chances are it's fixed > >> in https://github.com/sympy/sympy/pull/2126 though. > >> > >> Aaron Meurer > >> > >> On Tue, May 28, 2013 at 9:23 AM, Will Furnass > >> <[email protected]> wrote: > >> > Hi, > >> > > >> > I'm fairly new to sympy. I'm trying to evalute an integral > analytically > >> > over the range 0..oo but when I run the last line in the script below > I > >> > get > >> > the following error (using the sympy git head). > >> > > >> > CoercionFailed: can't convert DMP([[1], []], ZZ, ZZ[_a1,_b1]) of type > >> > <class > >> > 'sympy.polys.polyclasses.DMP'> from ZZ[_a1,_b1] to RR > >> > > >> > Anyone got any ideas as to what this means? > >> > > >> > Regards, > >> > > >> > Will Furnass > >> > > >> > > >> > ###### > >> > > >> > D, dx, k, L, n, P, Q, t, tau_a, tau_s, x= symbols('D dx k, L, n, P, > Q, > >> > t, > >> > \\tau_a, \\tau_s x') > >> > > >> > V = Q * 4 / (pi * (D**2)) > >> > > >> > expr1 = (tau_a - tau_s)**n * k > >> > expr2 = (t * P * (tau_a - tau_s)**n * n) - (t * P * (tau_a - > tau_s)**n) > >> > + (k > >> > * tau_a) - (k * tau_s) > >> > expr3 = 1 / (n-1) > >> > expr4 = P * (tau_a - tau_s)**n > >> > expr5 = (t * P * (tau_a - tau_s)**n * n) - (t * P * (tau_a - > tau_s)**n) > >> > + (k > >> > * tau_a) - (k * tau_s) > >> > expr6 = ((expr1 / expr2) ** expr3) * expr4 / expr5 > >> > expr7 = - P * exp(-t * P / k ) * (-tau_a + tau_s) / k > >> > expr8 = Piecewise((expr6, Ne(n,1)), (expr7, Eq(n,1))) > >> > > >> > T = Piecewise((0, t < 0), (k * D * pi * dx * expr8 / Q, t >= 0)) > >> > > >> > curve_expr = integrate(T(t - (x/V)), (x, 0, L)) > >> > > >> > vals = { > >> > P : 0.00022, > >> > k : 0.5, > >> > tau_s : 0.01, > >> > tau_a : 2.0, > >> > Q : 0.01, > >> > D : 0.125, > >> > L : 1225, > >> > n : 3.0, > >> > dx : 1} > >> > > >> > integrate(curve_expr.subs(vals)).eval() > >> > > >> > -- > >> > 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?hl=en-US. > >> > For more options, visit https://groups.google.com/groups/opt_out. > >> > > >> > > > > > -- > > 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] <javascript:>. > > To post to this group, send email to [email protected]<javascript:>. > > > Visit this group at http://groups.google.com/group/sympy?hl=en-US. > > For more options, visit https://groups.google.com/groups/opt_out. > > > > > -- You received this message because you are subscribed to the Google Groups "sympy" group. 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