Newton-Raphson-Method/newton_raphson_method.py at master · Toktom/Newton-Raphson-Method · GitHub

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import matplotlib.pyplot as plt
import numpy as np

if __name__ == "__main__":

    def function(x):
    """
    Function of the function.

        Parameters:
        -----------
            x : int | float
                var

        Returns:
        --------
            value : int | float
                calculated value of the function
    """
        value = x**2-2
        return value # The main function

    def derivative(x):
    """
    Derivative of the function.

        Parameters:
        -----------
            x : int | float
                var

        Returns:
        --------
            value : int | float
                calculated value of the derivative of the function
    """
        return 2*x  # The derivative of the main function

def newton(function, derivative, x0, tol, max_iter=100):
    """
    Calculate and plots the values througth newton-raphson method.

        Parameters:
        -----------
            function : function
                function
            derivative : function
                derivative
            x0: int | float
                x0
            tol: float
                tolerance
            max_iter: int
                number of the maximal iterations

        Returns:
        --------
            x1 : int | float
                calculated value of the function
    """
    x1 = 0

    if abs(x0-x1)<= tol and abs((x0-x1)/x0)<= tol:
        return x0

    print("k\t x0\t\t function(x0)")
    k = 1

    while k <= max_iter:
        x1 = x0 - (function(x0)/derivative(x0))
        print("x%d\t%e\t%e"%(k,x1,function(x1)))

        if abs(x0-x1)<= tol and abs((x0-x1)/x0)<= tol:
            plt.plot(x0, function(x0), 'or')
            return x1

        x0 = x1
        k = k + 1
        plt.plot(x0, function(x0), 'or')

        # Stops the method if it hits the number of maximum iterations
        if k > max_iter:
            print("ERROR: Exceeded max number of iterations")

    return x1  # Returns the value

sqrt = newton(function, derivative, 1.7, 0.0000001)
print("The approximate value of x is: "+str(sqrt))

# Plotting configuration
u = np.arange(1.0, 2.0, 0.0001) # Setting up values for x in the plot
w = u**2 - 2 # Define the main function again

plt.plot(u, w)
plt.axhline(y=0.0, color='black', linestyle='-')
plt.title('Newton-Raphson Graphics for' + ' y = x^2 - 2')
plt.xlabel('X')
plt.ylabel('Y')
plt.grid(True)
plt.legend(['Xn'], loc='upper left')
plt.show()