So here are two work-arounds:
A=find_minimum_on_interval(-x*sin(x),.5,2.5)
(-1)*A[0]
and
A=x*sin(x)
A.find_maximum_on_interval(.5,2.5)
- but neither of these is really satisfying. A function as fundamental as
max of a continuous function over an interval should not run into and error
message like
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "_sage_input_36.py", line 10, in <module>
exec compile(u'open("___code___.py","w").write("# -*- coding: utf-8 -*-\\n"
+
_support_.preparse_worksheet_cell(base64.b64decode("ZmluZF9tYXhpbXVtX29uX2ludGVydmFsKHgqc2luKHgpLC41LDIuNSk="),globals())+"\\n");
execfile(os.path.abspath("___code___.py"))
File "", line 1, in <module>
File
"/private/var/folders/h-/h-SNXV0qH8Ge-MkoSlEMtE+++TI/-Tmp-/tmpT70pnk/___code___.py",
line 3, in <module>
exec compile(u'find_maximum_on_interval(x*sin(x),_sage_const_p5
,_sage_const_2p5 )
File "", line 1, in <module>
File
"/Volumes/sage-4.7.1-OSX-64bit-10.6-x86_64-Darwin/Sage-4.7.1-OSX-64bit-10.6.app/Contents/Resources/sage/local/lib/python2.6/site-packages/sage/numerical/optimize.py",
line 127, in find_maximum_on_interval
minval, x = find_minimum_on_interval(lambda z: -f(z), a=a, b=b, tol=tol,
maxfun=maxfun)
File
"/Volumes/sage-4.7.1-OSX-64bit-10.6-x86_64-Darwin/Sage-4.7.1-OSX-64bit-10.6.app/Contents/Resources/sage/local/lib/python2.6/site-packages/sage/numerical/optimize.py",
line 186, in find_minimum_on_interval
xmin, fval, iter, funcalls = scipy.optimize.fminbound(f, a, b,
full_output=1, xtol=tol, maxfun=maxfun)
File
"/Volumes/sage-4.7.1-OSX-64bit-10.6-x86_64-Darwin/Sage-4.7.1-OSX-64bit-10.6.app/Contents/Resources/sage/local/lib/python2.6/site-packages/scipy/optimize/optimize.py",
line 1021, in fminbound
if fu <= fx:
File "expression.pyx", line 1852, in
sage.symbolic.expression.Expression.__nonzero__
(sage/symbolic/expression.cpp:8675)
File
"/Volumes/sage-4.7.1-OSX-64bit-10.6-x86_64-Darwin/Sage-4.7.1-OSX-64bit-10.6.app/Contents/Resources/sage/local/lib/python2.6/site-packages/sage/symbolic/relation.py",
line 403, in test_relation_maxima
s = m.parent()._eval_line('is (%s)'%repr(m))
File
"/Volumes/sage-4.7.1-OSX-64bit-10.6-x86_64-Darwin/Sage-4.7.1-OSX-64bit-10.6.app/Contents/Resources/sage/local/lib/python2.6/site-packages/sage/interfaces/maxima_lib.py",
line 420, in _eval_line
if statement: result = ((result + '\n') if result else '') +
max_to_string(maxima_eval("#$%s$"%statement))
File "ecl.pyx", line 691, in sage.libs.ecl.EclObject.__call__
(sage/libs/ecl.c:4622)
File "ecl.pyx", line 556, in sage.libs.ecl.EclObject.__init__
(sage/libs/ecl.c:4305)
File "ecl.pyx", line 387, in sage.libs.ecl.python_to_ecl
(sage/libs/ecl.c:3521)
File "ecl.pyx", line 365, in sage.libs.ecl.python_to_ecl
(sage/libs/ecl.c:3292)
File "ecl.pyx", line 282, in sage.libs.ecl.ecl_safe_read_string
(sage/libs/ecl.c:2805)
File "ecl.pyx", line 265, in sage.libs.ecl.ecl_safe_funcall
(sage/libs/ecl.c:2650)
RuntimeError: ECL says: THROW: The catch MACSYMA-QUIT is undefined.
On Thursday, May 24, 2012 2:44:07 PM UTC-4, MathLynx wrote:
>
> The code find_minimum_on_interval(x*sin(x),.5,2.5) works like a
> charm, giving (0.23971279031301418, 0.5000000228822995) as output.
>
> But the code find_maximum_on_interval(x*sin(x),.5,2.5) gives a mess.
> Plotting works fine ( plot(x*sin(x),(x,.5,2.5)) ).
>
> Is there some notational issue here? Some issue that works for min but
> not max?
>
> John A. Velling
>
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