Done. You should announce that tip to the list. There were indeed some good questions on there. SO is a good way to keep our collective ear to the ground.
On Fri, Apr 4, 2014 at 1:48 PM, Aaron Meurer <asmeu...@gmail.com> wrote: > Yes, you can go to http://stackexchange.com/filters/ and set up a filter > for the SymPy tag, and it will email you new questions. Lately there are > new questions almost every single day, so it would definitely help if > others were answering there as well. > > The questions on stackoverflow tend to be high quality and often have > rather interesting use-cases (there are doozies, of course, but the worst > questions are closed automatically). > > Aaron Meurer > > > On Tue, Apr 1, 2014 at 9:48 AM, Matthew Rocklin <mrock...@gmail.com>wrote: > >> First, thanks for posting the question on stack overflow, I think that we >> should use that more. Unfortunately, few of us (maybe only Aaron?) >> actually checks SO, again, I think that we should use it more. >> >> Sympy.stats is producing an integral that looks like the following: >> In [1]: from sympy.stats import * >> In [2]: a, b, c, d, = symbols('a b c d', real=True, positive=True) >> In [3]: G1 = GammaInverse("G1", a, b) >> In [4]: G2 = GammaInverse("G2", c, d) >> In [5]: G3 = S(7)/10*G1 + S(3)/10*G2 >> In [7]: density(G3, evaluate=False)(x) >> Out[7]: >> ∞ >> >> ⌠ >> >> ⎮ ∞ >> >> ⎮ ⌠ >> >> ⎮ ⎮ -b >> >> ⎮ ⎮ ─── >> >> ⎮ -d ⎮ -a - 1 a G₁ ⎛7⋅G₁ 3⋅G₂ ⎞ >> >> ⎮ ─── ⎮ G₁ ⋅b ⋅ℯ ⋅DiracDelta⎜──── + ──── - x⎟ >> >> ⎮ -c - 1 c G₂ ⎮ ⎝ 10 10 ⎠ >> >> ⎮ G₂ ⋅d ⋅ℯ ⋅⎮ ──────────────────────────────────────────── d(G₁) >> >> ⎮ ⎮ Γ(a) >> >> ⎮ ⌡ >> >> ⎮ 0 >> >> ⎮ ───────────────────────────────────────────────────────────────────── >> d(G₂) >> ⎮ Γ(c) >> >> ⌡ >> >> 0 >> >> >> So one could reduce your question into a question like, "does anyone have >> any thoughts on how SymPy could solve this integral?" >> >> >> On Tue, Apr 1, 2014 at 6:26 AM, John Griffiths < >> j.davidgriffi...@gmail.com> wrote: >> >>> >>> >>> Does anyone have any thoughts on how to solve this problem: >>> >>> When I try to take a weighted mixture of inverse gamma distributions >>> using sympy.stats I get the following error >>> >>> %matplotlib inlinefrom matplotlib import pyplot as pltfrom sympy.stats >>> import GammaInverse, densityimport numpy as np >>> >>> f1 = 0.7; f2 = 1-f1 >>> G1 = GammaInverse("G1", 5, 120/(5.5*2.5E-7)) >>> G2 = GammaInverse("G2", 4, 120/(5.5*1.5E-7)) >>> G3 = f1*G1 + f2*G2 >>> D1 = density(G1); >>> D2 = density(G2); >>> D3 = density(G3); >>> v1 = [D1(i).evalf() for i in u] >>> v2 = [D2(i).evalf() for i in u] >>> v3 = [D3(i).evalf() for i in u] >>> >>> ...which errors at D3 = density(G3). The error includes >>> >>> PolynomialDivisionFailed: couldn't reduce degree in a polynomial >>> division algorithm when dividing >>> [231761.370742578/(0.0011381138741823*G2**2 - >>> 0.007587425827882*G2*_z + 0.0126457097131367*_z**2), 0.0] >>> by [263.770831541635/263.770831541635, 0.0]. >>> This can happen when it's not possible to detect zero in the coefficient >>> domain. The domain of computation is RR(G2,_t0,_z). Zero detection is >>> guaranteed in this >>> coefficient domain. This may indicate a bug in SymPy or the domain is user >>> definedand doesn't implement zero detection properly. >>> >>> (also get this when I take mixture of inverse Gamma with Normal and >>> Uniform distributions) >>> >>> Should this be possible? >>> >>> >>> Cheers. >>> >>> >>> >>> (p.s. apologies for redundancy with recent SO post) >>> >>> >>> >>> -- >>> 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 sympy+unsubscr...@googlegroups.com. >>> To post to this group, send email to sympy@googlegroups.com. >>> 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/4cb36d1b-6827-4123-8efe-b1462d822e6b%40googlegroups.com<https://groups.google.com/d/msgid/sympy/4cb36d1b-6827-4123-8efe-b1462d822e6b%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 sympy+unsubscr...@googlegroups.com. >> To post to this group, send email to sympy@googlegroups.com. >> 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/CAJ8oX-HEDx4fraBRj4HARPaCEJKXKaTP3zjS_dbeqd3WoeAAWA%40mail.gmail.com<https://groups.google.com/d/msgid/sympy/CAJ8oX-HEDx4fraBRj4HARPaCEJKXKaTP3zjS_dbeqd3WoeAAWA%40mail.gmail.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 sympy+unsubscr...@googlegroups.com. > To post to this group, send email to sympy@googlegroups.com. > 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%3D6JUTWn5vz7oih7%2BY18j6jNbvxZD4uEy0L9zTtp4-f3www%40mail.gmail.com<https://groups.google.com/d/msgid/sympy/CAKgW%3D6JUTWn5vz7oih7%2BY18j6jNbvxZD4uEy0L9zTtp4-f3www%40mail.gmail.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. 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