#3863: numerical integration of x^2.7 * e^(-2.4*x) fails
----------------------+-----------------------------------------------------
Reporter: ddrake | Owner: gfurnish
Type: defect | Status: new
Priority: major | Milestone: sage-4.0.1
Component: calculus | Keywords: integration integral calculus symbolic
----------------------+-----------------------------------------------------
Comment(by kcrisman):
The essential problem is that with half-integer or integer exponents of x,
Maxima can symbolically integrate this using Erf. Otherwise it can't
(that doesn't mean it's not possible, just that Maxima doesn't know).
Before, Sage tried to turn the expression into a complex one if it
couldn't evaluate it, but that doesn't do much for a real (unevaluated)
integral; now the new symbolics just complain that it's not numeric, which
of course it isn't.
My view is that the correct fix is to put some kind of check in for when
"integrate" is part of the output string fed into .n() and in that case at
least attempt to use numerical_integral or something. Of course that has
the problem that things like
{{{
sage: integrate(1/(1+x^7))
1/7*log(x + 1) - 1/7*integrate((x^5 - 2*x^4 + 3*x^3 - 4*x^2 + 5*x -
6)/(x^6 - x^5 + x^4 - x^3 + x^2 - x + 1), x)
}}}
Maxima is able to partly symbolically integrate, leaving
{{{
sage: integrate(1/(1+x^7),x,0,1)
}}}
in trouble. But at least a check for "integrate" at the beginning could
help.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/3863#comment:2>
Sage <http://sagemath.org/>
Sage - Open Source Mathematical Software: Building the Car Instead of
Reinventing the Wheel
--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"sage-trac" group.
To post to this group, send email to [email protected]
To unsubscribe from this group, send email to
[email protected]
For more options, visit this group at
http://groups.google.com/group/sage-trac?hl=en
-~----------~----~----~----~------~----~------~--~---
