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] <javascript:>> 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()
> >
> > --
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