CODEWITHSUNDEEP
pythonnumpyscipy
David Vivas
David Vivas

Reputation: 77

define an harmonic oscillator function to use in odeint

I'm triying to write an ode to solve an harmonic oscillator problem and I have this problem with my function harmonic to use in odeint command. 

import matplotlib.pyplot as plt
import numpy as np
from scipy.integrate import odeint

k=4.0
m=1.0
B=0

def harmonic((x, y), t):
    return [y, -k * x / m + B / m * y]

Gives the error message:

  File "<ipython-input-60-2d6b156227be>", line 1
    def harmonic((x, y), t):
                 ^
SyntaxError: invalid syntax

Someone can help me? Thank you!

Upvotes: 1

Views: 1079

Answers (2)

bubble
bubble

Reputation: 1672

Look at the following example:

import matplotlib.pyplot as plt
import numpy as np
from scipy.integrate import odeint

k = 4.0
m = 1.0
B = 0

def harmonic(var, t=None):
    x, y = var[0], var[1] # var is assumed to be an array, usually numpy array
    return [y, -k * x / m + B / m * y]

result = odeint(harmonic, (0.2, 0), np.linspace(0, 1, 100))
plt.plot(result[:,0], result[:,1], 'r-')
plt.show()

enter image description here

Upvotes: 2

amanb
amanb

Reputation: 5473

(x, y) represents a tuple. If you want to just use x,y as individual variables, simply use x,y. Your function will look like this:

def harmonic(x, y, t):
    return [y, -k * x / m + B / m * y]

Passing hypothetical values for x,y & t to the harmonic function returns the list calculated by the code in the return statement of the function:

harmonic(2,3,5)
#Output:
[3, -8.0]

Upvotes: 1

Related Questions