CODEWITHSUNDEEP
python-3.xsympyderivative
Alistair
Alistair

Reputation: 1

Python partial derivative

I am trying to put numbers in a function that has partial derivatives but I can't find a correct way to do it,I have searched all the internet and I always get an error.Here is the code:

from sympy import symbols,diff
import sympy as sp
import numpy as np
from scipy.misc import derivative
a, b, c, d, e, g, h, x= symbols('a b c d e g h x', real=True)
da=0.1
db=0.2
dc=0.05
dd=0
de=0
dg=0
dh=0
f = 4*a*b+a*sp.sin(c)+a**3+c**8*b
x = sp.sqrt(pow(diff(f, a)*da, 2)+pow(diff(f, b)*db, 2)+pow(diff(f, c)*dc, 2))
def F(a, b, c):
return x

print(derivative(F(2 ,3 ,5)))

I get the following error: derivative() missing 1 required positional argument: 'x0'

I am new to python so maybe it's a stupid question but I would feel grateful if someone helped me.

Upvotes: 0

Views: 5676

Answers (2)

Pranav Kumar
Pranav Kumar

Reputation: 354

I have used a python package 'sympy' to perform the partial derivative. The point at which the partial derivative is to be evaluated is val. The argument 'val' can be passed as a list or tuple.

# Sympy implementation to return the derivative of a function in x,y
# Enter ginput as a string expression in x and y and val as 1x2 array

def partial_derivative_x_y(ginput,der_var,val):
    import sympy as sp
    x,y = sp.symbols('x y')
    function = lambda x,y: ginput
    derivative_x = sp.lambdify((x,y),sp.diff(function(x,y),x))
    derivative_y = sp.lambdify((x,y),sp.diff(function(x,y),y))
    if der_var == 'x' :
        return derivative_x(val[0],val[1])
    if der_var == 'y' :
        return derivative_y(val[0],val[1])

 input1 = 'x*y**2 + 5*log(x*y +x**7) + 99'
 partial_derivative_x_y(input1,'y',(3,1))

Upvotes: 0

Stanislav Ivanov
Stanislav Ivanov

Reputation: 1974

You can find three partial derivatives of function foo by variables a, b and c at the point (2,3,5): 

f = 4*a*b+a*sp.sin(c)+a**3+c**8*b
foo = sp.sqrt(pow(diff(f, a)*da, 2)+pow(diff(f, b)*db, 2)+pow(diff(f, c)*dc, 2))

foo_da = diff(foo, a)
foo_db = diff(foo, b)
foo_dc = diff(foo, c)

print(foo_da," = ", float(foo_da.subs({a:2, b:3, c:5})))
print(foo_db," = ", float(foo_db.subs({a:2, b:3, c:5})))
print(foo_dc," = ", float(foo_dc.subs({a:2, b:3, c:5})))

Upvotes: 1

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