# Requires 'control' package:
# pip install control
import numpy as np
import matplotlib.pyplot as plt
import control as ctrl

def nyquist_diagram(T):
    # Define the numerator and denominator of the transfer function
    numerator = [1]  # Numerator of the transfer function
    den1 = [1, 1, 1]  # First part of the denominator
    den2 = [T, 1]  # Second part of the denominator

    # Convolve the two denominator parts
    denominator = np.convolve(den1, den2)

    # Create the transfer function
    system = ctrl.TransferFunction(numerator, denominator)
    
    # Generate the Nyquist plot
    ctrl.nyquist_plot(system)
    
    # Enhance plot appearance
    plt.title('Nyquist Diagram')
    plt.xlabel('Real')
    plt.ylabel('Imaginary')
    plt.grid(True)
    plt.show()

# Example usage
T = 1  # Time constant
nyquist_diagram(T)