Solving an equation with scipy's fsolve

Question

I'm trying to solve the equation f(x) = x-sin(x) -n*t -m0

In this equation, n and m0 are attributes, defined in my class. Further, t is a constant integer in the equation, but it has to change each time.

I've solved the equation so i get a 'new equation'. I've imported scipy.optimize

def f(x, self):
    return (x - math.sin(x) -self.M0 - self.n*t)

def test(self,t):
    return fsolve(self.f, 1, args=(t))

Any corrections and suggestions to make it work?

Answer 1

I can see at least two problems: you've mixed up the order of arguments to f, and you're not giving f access to t. Something like this should work:

import math
from scipy.optimize import fsolve

class Fred(object):
    M0 = 5.0
    n = 5

    def f(self, x, t):
        return (x - math.sin(x) -self.M0 - self.n*t)

    def test(self, t):
        return fsolve(self.f, 1, args=(t))

[note that I was lazy and made M0 and n class members]

which gives:

>>> fred = Fred()
>>> fred.test(10)
array([ 54.25204733])
>>> import numpy
>>> [fred.f(x, 10) for x in numpy.linspace(54, 55, 10)]
[-0.44121095114838482, -0.24158955381855662, -0.049951288133726734,
 0.13271070588400136, 0.30551399241764443, 0.46769772292130796, 
 0.61863201965219616, 0.75782574394219182, 0.88493255340251409, 
 0.99975517335862207]