Don't worry, a lot of people miss the chop option. We should probably add a note about it to the evalf section of the tutorial. http://docs.sympy.org/latest/tutorial/basic_operations.html#evalf.
Aaron Meurer On Sun, Nov 3, 2013 at 11:10 PM, Alexander Birukov <[email protected]> wrote: > Oh, sorry. > > chop=<bool> > Replace tiny real or imaginary parts in subresults > by exact zeros (default=False) > > No idea how I missed it. Instead, I was trying to make n/precision lower and > round it. > > Thanks for your help again. > > понедельник, 4 ноября 2013 г., 7:59:59 UTC+4 пользователь Aaron Meurer > написал: >> >> When evalf gives such a small number, it is zero. The precision of >> evalf by default is 15 digits, so 10**-140 and 0 are no different at >> that precision. >> >> You can make evalf automatically reduce such small numbers by passing >> chop=True, like log(x, 2).evalf(subs={x: 1}, chop=True). >> >> Aaron Meurer >> >> >> On Sun, Nov 3, 2013 at 2:04 PM, Alexander Birukov <[email protected]> >> wrote: >> > I dont really understand why it happens, although solve(log(x, 2)) gives >> > 1 >> > as an answer. I'd use solve for sure, but unfortunetly, I have to >> > calculate >> > expression with different x. >> > Any solution to fix this? >> > >> > -- >> > 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. >> > 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]. > To post to this group, send email to [email protected]. > Visit this group at http://groups.google.com/group/sympy. > 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]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/sympy. For more options, visit https://groups.google.com/groups/opt_out.
