CODEWITHSUNDEEP
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Atharva Pathak
Atharva Pathak

Reputation: 3

Args not being passed to Scipy solve_ivp

I have copy-and-pasted the Lotka-Volterra example for Scipy's solve_ivp function from the documentation here, but I get the error

lotkavolterra() missing 4 required positional arguments: 'a', 'b', 'c', and 'd'

It seems to me that the arguments aren't being passed to lotkavolterra despite it "example of a system with additional parameters". The code is below.

from scipy.integrate import solve_ivp

def lotkavolterra(t, z, a, b, c, d):
    x, y = z
    return [a*x - b*x*y, -c*y + d*x*y]

sol = solve_ivp(lotkavolterra, [0, 15], [10, 5], args=(1.5, 1, 3, 1), dense_output=True)

print(sol)

How do I resolve my issue?

Upvotes: 0

Views: 433

Answers (1)

joni
joni

Reputation: 7157

If your version of solve_ivp doesn't provide the args argument, you can use a lambda function:

sol = solve_ivp(lambda t, z: lotkavolterra(t, z, 1.5, 1, 3, 1), [0, 15], [10, 5], dense_output=True)

However, it's highly recommended to update your scipy version, like Warren already hinted in the comments.

Upvotes: 1

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