This is the list... Aaron Meurer
On Fri, Apr 4, 2014 at 4:17 PM, Matthew Rocklin <mrock...@gmail.com> wrote: > 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. > 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-EUvvPMJhPMb6FqoyuxY9MS2OLGavnHavgH0dQLBaBjpQ%40mail.gmail.com<https://groups.google.com/d/msgid/sympy/CAJ8oX-EUvvPMJhPMb6FqoyuxY9MS2OLGavnHavgH0dQLBaBjpQ%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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