I get some trouble, if I want to pass a float to mpmath.mpf and find the root with mp.findroot.
The problem continues the story of a previous question: Polynomial function cannot be solved by Python sympy
import sympy
omega = sympy.symbols('omega')
from sympy import I
import mpmath as mp
import numpy as np
# Definition of simplified function
def function(omega):
return sympy.Poly((-1.16*omega**4), omega)
# This function does not work
def doesntwork(omega):
return (mp.mpf(str(np.real(sympy.lambdify( (I),function(omega).coeffs()[0])(1j)))) * omega ** 4)
# This function does work, but I need to handover the value due to its not constant
def doeswork(omega):
return (mp.mpf('-1.16') * omega ** 4)
#print mp.findroot(doesntwork, 1) # error message
print mp.findroot(doeswork, 1) # result is obtained
The mp.findroot command does work if I enter the coefficient with a string, but does not work if I read the coefficient by an automatic procedure. The problem seems to be caused by the input to mpmath.mpf which is not recognized as string. I need this automatic procedure, because the coefficients are not constant as in this simple example.
The error message for the function doesntwork is:
---------------------------------------------------------------------------
AttributeError Traceback (most recent call last)
<ipython-input-44-7ed2fe96e32b> in <module>()
----> 1 print mp.findroot(doesntwork, 1) # error message
2 #print mp.findroot(doeswork, 1) # result is obtained
C:\Anaconda\lib\site-packages\mpmath\calculus\optimization.pyc in findroot(ctx, f, x0, solver, tol, verbose, verify, **kwargs)
926 # detect multidimensional functions
927 try:
--> 928 fx = f(*x0)
929 multidimensional = isinstance(fx, (list, tuple, ctx.matrix))
930 except TypeError:
<ipython-input-40-f85df4161c52> in doesntwork(omega)
1 # This function does not work
2 def doesntwork(omega):
----> 3 return (mp.mpf(str(np.real(sympy.lambdify( (I),function(omega).coeffs()[0])(1j)))) * omega ** 4)
4
5 # This function does work, but I need to handover the value due to its not constant
<ipython-input-39-fb50e638fea4> in function(omega)
1 # Definition of simplified function
2 def function(omega):
----> 3 return sympy.Poly((-1.16*omega**4), omega)
C:\Anaconda\lib\site-packages\sympy\polys\polytools.pyc in __new__(cls, rep, *gens, **args)
71 def __new__(cls, rep, *gens, **args):
72 """Create a new polynomial instance out of something useful. """
---> 73 opt = options.build_options(gens, args)
74
75 if 'order' in opt:
C:\Anaconda\lib\site-packages\sympy\polys\polyoptions.pyc in build_options(gens, args)
729
730 if len(args) != 1 or 'opt' not in args or gens:
--> 731 return Options(gens, args)
732 else:
733 return args['opt']
C:\Anaconda\lib\site-packages\sympy\polys\polyoptions.pyc in __init__(self, gens, args, flags, strict)
152 self[option] = cls.preprocess(value)
153
--> 154 preprocess_options(args)
155
156 for key, value in dict(defaults).items():
C:\Anaconda\lib\site-packages\sympy\polys\polyoptions.pyc in preprocess_options(args)
150
151 if value is not None:
--> 152 self[option] = cls.preprocess(value)
153
154 preprocess_options(args)
C:\Anaconda\lib\site-packages\sympy\polys\polyoptions.pyc in preprocess(cls, gens)
290 elif has_dups(gens):
291 raise GeneratorsError("duplicated generators: %s" % str(gens))
--> 292 elif any(gen.is_commutative is False for gen in gens):
293 raise GeneratorsError("non-commutative generators: %s" % str(gens))
294
C:\Anaconda\lib\site-packages\sympy\polys\polyoptions.pyc in <genexpr>((gen,))
290 elif has_dups(gens):
291 raise GeneratorsError("duplicated generators: %s" % str(gens))
--> 292 elif any(gen.is_commutative is False for gen in gens):
293 raise GeneratorsError("non-commutative generators: %s" % str(gens))
294
AttributeError: 'mpf' object has no attribute 'is_commutative'
Thank you for your help!
