On 02/09/2010 04:10 PM, Giovanni Lanzani wrote:
"[email protected]"<[email protected]> writes:
sage: def theta(dz):
... angle=0;
... if 0<=dz<2*r*cot(gangle) : angle= 2*arcsin(dz*tan(gangle)/2/r);
... if 2*r*cot(gangle)<= dz< 2*2*r*cot(gangle) : angle=
2*arcsin((dz-2*r*cot(gangle))/(cot(gangle)*2*r)) - pi;
... if 2*2*r*cot(gangle)<= dz< 4*2*r*cot(gangle) : angle=
2*arcsin((dz-2*2*r*cot(gangle))/(cot(gangle)*2*r)) - 2*pi;
... if 0>=dz>-2*r*cot(gangle) : angle= 2*arcsin(dz*tan(gangle)/2/r);
... if 2*r*cot(gangle)>= dz> -2*2*r*cot(gangle) : angle=
2*arcsin((dz+2*r*cot(gangle))/(cot(gangle)*2*r)) - pi;
... if 2*2*r*cot(gangle)>= dz> -4*2*r*cot(gangle) : angle=
2*arcsin((dz+2*2*r*cot(gangle))/(cot(gangle)*2*r)) - 2*pi;
... return angle;
...
then executing
sage: find_root(erseno(x)==0,2,10,xtol=0.01)
Try to print erseno(x)
it seems that your equation becomes 0.609368485026990==0
It probably does because I put angle=0 at the beginning of theta(dz). If
I take it away I get (if calling erseno(x))
->Traceback (most recent call last):
-> File "<stdin>", line 1, in<module>
-> File "_sage_input_16.py", line 4, in<module>
-> open("___code___.py","w").write("# -*- coding: utf-8 -*-\n" +
_support_.preparse_worksheet_cell(base64.b64decode("ZmluZF9yb290KGVyc2Vubyh4KSwyLDEwLHh0b2w9MC4wMSk="),globals())+"\n");
execfile(os.path.abspath("___code___.py"))
-> File "", line 1, in<module>
->
-> File
"/private/var/folders/bc/bcpFbanYErusTUkLXieJfE+++TI/-Tmp-/tmpy0Ob9z/___code___.py",
line 3, in<module>
-> find_root(erseno(x),_sage_const_2 ,_sage_const_10 ,xtol=_sage_const_0p01
)
-> File "", line 1, in<module>
->
-> File
"/private/var/folders/bc/bcpFbanYErusTUkLXieJfE+++TI/-Tmp-/tmp87jRdJ/___code___.py",
line 4, in erseno
-> return _sage_const_2 *arcsin(b*sin(gangle)/_sage_const_2
/r)-(Nrib-_sage_const_1 )*theta(dz2(x))/_sage_const_2 -(Nrib+_sage_const_1
)*theta(x)/_sage_const_2 ;
-> File
"/private/var/folders/bc/bcpFbanYErusTUkLXieJfE+++TI/-Tmp-/tmps88obK/___code___.py",
line 11, in theta
-> return angle;
->UnboundLocalError: local variable 'angle' referenced before assignment
So which of your "if" conditions is true when the input is the variable
x? I think that's the problem---none of the conditions is true, so
angle is never set, so you are trying to return an undefined variable.
The find_root function takes in just a function (not a function
evaluated at x), so the call should look something like:
find_root(erseno, xmin, xmax)
However, it seems that there is another problem with a NaN coming up. I
just posted about this in another thread.
Thanks,
Jason
--
Jason Grout
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