Status: Accepted
Owner: [email protected]
Labels: Type-Defect Priority-Medium
New issue 2343 by [email protected]: as_poly returns None
http://code.google.com/p/sympy/issues/detail?id=2343
Here is an expression in x and y
h[1] >>> q1
-1 + (1/2 - x/2)**2 + (1/3 - y/3)**2
h[2] >>> _.as_poly(x,y)
It didn't become a poly. Let's sympify the string form and try again:
h[2] >>> S(str(q1)).as_poly(x,y)
Poly(1/4*x**2 - 1/2*x + 1/9*y**2 - 2/9*y - 23/36, x, y, domain='QQ')
It worked!? Try expanding q1 and trying
h[3] >>> q1.expand()
-23/36 - 2*y/9 - x/2 + x**2/4 + y**2/9
h[4] >>> _.as_poly(x,y)
It failed...is it the denominator issue?
h[4] >>> q1.expand()*36
-23 - 18*x - 8*y + 4*y**2 + 9*x**2
h[5] >>> _.as_poly(x,y)
No, that fails, too.
solve_polys_system fails because of this failure to create a poly from such
expressions. e.g.
h[1] >>> e1=Ellipse((1,1),2,3)
h[1] >>> e2=Ellipse((2,3),1,4)
h[1] >>> q1=e1.equation()
h[1] >>> q2=e2.equation()
h[1] >>> solve([q1,q2],[x,y])
this is the print put in the area of failure showing the 'g' for
which a conversion to poly was attempted at line 364 in solvers.py
g symbols g.has(s) for s in symbols
------------------------------------ ------ -----------------------
-1 + (1/2 - x/2)**2 + (1/3 - y/3)**2, [x, y], [True, True]
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "sympy\solvers\solvers.py", line 371, in solve
raise NotImplementedError()
NotImplementedError
What is the solution to this problem?
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