On 2015-03-10, M M <mirettemarz...@gmail.com> wrote: > I get different results from Sage when I try to get a numerical > approximation for an expression and if I use evaluate a preparse of the > string. I get different results on different versions of sage as well. Here > are samples:
Integration is done by Maxima, and it is a bloody mess; e.g. (with Sage 6.6.beta3) sage: numerical_integral(x/(x^3-x+1.), 1., 2.) (0.565799916456428, 6.281640945809164e-15) sage: integral(x/(x^3-x+1), x, 1, 2).n() 1.11396858782562 sage: integral(x/(x^3-x+1), x, 1, 2).full_simplify().n() 0.168522351678247 sage: Do you know which one is actually correct? It looks like the 2nd one might be right (by looking at sage: plot(x/(x^3-x+1), x, 1, 2)) PS. .n() is the same as numerical_approx() > > ---------------------------------------------------------------------- > >| Sage Version 5.3, Release Date: 2012-09-08 | > >| Type "notebook()" for the browser-based notebook interface. | > >| Type "help()" for help. | > > ---------------------------------------------------------------------- > > sage: eval(preparse("numerical_approx(integral(x/(x^3-x+1), x, 1, 2))")) > > 0.132008722884722 > > sage: numerical_approx(integral(x/(x^3-x+1), x, 1, 2)) > > 0.132008722884722 > > sage: A = integral(x/(x^3-x+1), x, 1, 2) > > sage: A_str = str(A) > > sage: eval(preparse("numerical_approx("+A_str +")")) > > -0.393296585552547 > > sage: > > > ┌────────────────────────────────────────────────────────────────────┐ > │ Sage Version 6.5, Release Date: 2015-02-17 │ > │ Type "notebook()" for the browser-based notebook interface. │ > │ Type "help()" for help. │ > └────────────────────────────────────────────────────────────────────┘ > sage: eval(preparse("numerical_approx(integral(x/(x^3-x+1), x, 1, 2))")) > 1.45943044687563 > sage: numerical_approx(integral(x/(x^3-x+1), x, 1, 2)) > 1.45943044687563 > sage: A = integral(x/(x^3-x+1), x, 1, 2) > sage: > sage: A_str = str(A) > sage: > sage: eval(preparse("numerical_approx("+A_str +")")) > 0.159046901967485 > sage: > > ┌────────────────────────────────────────────────────────────────────┐ > │ Sage Version 6.2, Release Date: 2014-05-06 │ > │ Type "notebook()" for the browser-based notebook interface. │ > │ Type "help()" for help. │ > └────────────────────────────────────────────────────────────────────┘ > sage: eval(preparse("numerical_approx(integral(x/(x^3-x+1), x, 1, 2))")) > 1.64714767119638 > sage: numerical_approx(integral(x/(x^3-x+1), x, 1, 2)) > 1.64714767119638 > sage: A = integral(x/(x^3-x+1), x, 1, 2) > sage: A_str = str(A) > sage: eval(preparse("numerical_approx("+A_str +")")) > 0.162416510011260 > sage: > > > On the Notebook on the cloud it gives me the following error although the > version is the same as one of the versions I tried locally > version() > 'Sage Version 6.5, Release Date: 2015-02-17' > > numerical_approx(integral(x/(x^3-x+1), x, 1, 2)) > Error in lines 1-1 Traceback (most recent call last): File > "/projects/f700a2f3-7f30-4b47-9f18-e0309eb8c48c/.sagemathcloud/sage_server.py", > > line 875, in execute exec compile(block+'\n', '', 'single') in namespace, > locals File "", line 1, in <module> File "<string>", line 1, in <module> > File > "/usr/local/sage/sage-6.5/local/lib/python2.7/site-packages/sage/misc/functional.py", > > line 1298, in numerical_approx return x._numerical_approx(prec, > algorithm=algorithm) File "sage/symbolic/expression.pyx", line 4861, in > sage.symbolic.expression.Expression._numerical_approx > (build/cythonized/sage/symbolic/expression.cpp:27184) x = > self._convert(kwds) File "sage/symbolic/expression.pyx", line 1034, in > sage.symbolic.expression.Expression._convert > (build/cythonized/sage/symbolic/expression.cpp:7790) cdef GEx res = > self._gobj.evalf(0, kwds) ValueError: power::eval(): division by zero > > -- You received this message because you are subscribed to the Google Groups "sage-support" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-support+unsubscr...@googlegroups.com. To post to this group, send email to sage-support@googlegroups.com. Visit this group at http://groups.google.com/group/sage-support. For more options, visit https://groups.google.com/d/optout.