On Wed, Mar 11, 2015 at 2:38 AM, Kalevi Suominen <[email protected]> wrote: > > > On Wednesday, March 11, 2015 at 6:59:33 AM UTC+2, Aaron Meurer wrote: >> >> So perhaps you would have better results if you started with a Float >> with higher precision, like Float("0.07071", 100). > > > The floats are of the order 10**(-19000) in both the numerator and the > denominator before rounding.
Oh, that's a bit high. Is it possible to do the stabilization automatically? Aaron Meurer > >> >> On Sun, Feb 8, 2015 at 2:57 PM, Kalevi Suominen <[email protected]> wrote: >> > >> > >> > On Sunday, February 8, 2015 at 12:06:46 AM UTC+2, Sten Sogaard wrote >> >> >> >> >> >> H = 1/(0.07071*s**2 + 258.0*s + 1100000.) >> >> inverse_laplace_transform(1/s*H,s,t) >> >> >> >> >> >> Any ideas? >> > >> > >> > The current implementation leads to floating point numbers with very >> > large >> > positive and negative exponents. After the small numbers are rounded to >> > zero, nan results. >> > >> > However, the computation succeeds with suitably normalized coefficients: >> > ``` >> > In [38]: H1 = H.subs(s, 10000.*s) >> > In [40]: print(inverse_laplace_transform(1/s*H1, s, t)) >> > -1.0*(-9.09090909090909e-7*exp(0.182435299109037*t) + >> > 4.74279450417556e-7*sin(0.349688926583877*t) + >> > >> > 9.09090909090909e-7*cos(0.349688926583877*t))*exp(-0.182435299109037*t)*Heaviside(t) >> > ``` >> > (Of course, the result has to be normalized again.) >> > >> > For a more satisfactory solution, cancellation of exponents in the >> > intermediate results would be required. >> > >> > -- >> > 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/83a765a9-c984-4fa2-bbc2-00010e02ed83%40googlegroups.com. >> > >> > 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/4b49a4ae-ec3b-4ba5-acec-425e65865c3f%40googlegroups.com. > > 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%3D6KyV-wyvov%2B33rLwR3Nhmsg_K3%2BRg5EniCWcbD9qXJBFw%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
