Hi
I have previously solved this problem using odesolve from scipy.
I am now learning SAGE.
What is wrong here? I get zerodivision from SAGE but it had a solution
in odesolve.
t = var('t')
z = function('z',t)
y1= function('y1',t)
y2= function('y2',t)
b = 0.03; r1 = 6.0; r2 = 0.5; gamma = 0.01; ro = 6.0;
De1 = diff(z,t) - b + (r1*y1 + r2*y2 + b - (gamma*y2)*z) == 0
De2 = diff(y1,t)-(r1*y1+r2*y2)*z + (ro+b-gamma*y2)*y1 == 0
De3 = diff(y2,t)-ro*y1+gamma*y2*(1-y2)+y2*b == 0
desolve_system([De1, De2, De3], [z, y1, y2])
I get this result:
Traceback (click to the left for traceback)
...
ZeroDivisionError: Symbolic division by zero
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/var/autofs/misc/home/amsalework/.sage/sage_notebook/
worksheets/admin/13/code/1.py", line 17, in <module>
desolve_system([De1, De2, De3], [z, y1, y2])
File "", line 1, in <module>
File "/usr/local/src/sage-4.1.1/local/lib/python2.6/site-packages/
sage/calculus/desolvers.py", line 259, in desolve_system
soln[i] = sol.sage()
File "/usr/local/src/sage-4.1.1/local/lib/python2.6/site-packages/
sage/interfaces/expect.py", line 1578, in sage
return self._sage_()
File "/usr/local/src/sage-4.1.1/local/lib/python2.6/site-packages/
sage/interfaces/maxima.py", line 1703, in _sage_
return symbolic_expression_from_maxima_string(repr(self))
File "/usr/local/src/sage-4.1.1/local/lib/python2.6/site-packages/
sage/calculus/calculus.py", line 1677, in
symbolic_expression_from_maxima_string
return symbolic_expression_from_string(s, syms,
accept_sequence=True)
File "/usr/local/src/sage-4.1.1/local/lib/python2.6/site-packages/
sage/calculus/calculus.py", line 1774, in
symbolic_expression_from_string
return parse_func(s)
File "parser.pyx", line 516, in
sage.misc.parser.Parser.parse_sequence (sage/misc/parser.c:3803)
File "parser.pyx", line 531, in
sage.misc.parser.Parser.parse_sequence (sage/misc/parser.c:3689)
File "parser.pyx", line 602, in sage.misc.parser.Parser.p_sequence
(sage/misc/parser.c:4394)
File "parser.pyx", line 692, in sage.misc.parser.Parser.p_eqn (sage/
misc/parser.c:5101)
File "parser.pyx", line 728, in sage.misc.parser.Parser.p_expr (sage/
misc/parser.c:5382)
File "parser.pyx", line 761, in sage.misc.parser.Parser.p_term (sage/
misc/parser.c:5605)
File "parser.pyx", line 803, in sage.misc.parser.Parser.p_factor
(sage/misc/parser.c:5966)
File "parser.pyx", line 830, in sage.misc.parser.Parser.p_power
(sage/misc/parser.c:6077)
File "parser.pyx", line 884, in sage.misc.parser.Parser.p_atom (sage/
misc/parser.c:6525)
File "parser.pyx", line 920, in sage.misc.parser.Parser.p_args (sage/
misc/parser.c:6924)
File "parser.pyx", line 951, in sage.misc.parser.Parser.p_arg (sage/
misc/parser.c:7223)
File "parser.pyx", line 728, in sage.misc.parser.Parser.p_expr (sage/
misc/parser.c:5382)
File "parser.pyx", line 771, in sage.misc.parser.Parser.p_term (sage/
misc/parser.c:5721)
File "element.pyx", line 1271, in
sage.structure.element.RingElement.__div__ (sage/structure/element.c:
10502)
File "expression.pyx", line 1884, in
sage.symbolic.expression.Expression._div_ (sage/symbolic/
expression.cpp:10818)
ZeroDivisionError: Symbolic division by zero
regards,
Amsale
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