# %% Import of packages:

import numpy as np
import matplotlib.pyplot as plt

# %% Def of objective function:

def fun_f(x, L):
    A = (L/2 - x)*x
    f = -A
    return f

# %% Model param:
    
L = 40  # [m]

# %% Calculating f(x) for a number of x values:

x_lb = 0
x_ub = L/2
N_x = 100
x_array = np.linspace(x_lb, x_ub, N_x)

f_array = fun_f(x_array, L)  # Vectorized function call

# %% Plotting f(x):

plt.close('all')  # Closes all figures before plotting
plt.figure(num=1, figsize=(12, 9))  # Inches
plt.plot(x_array, f_array, '.', label='f = -A')
plt.legend()
plt.xlabel('x [m]')
plt.ylabel('[m2]')
plt.grid()

# plt.savefig('plot_square.pdf')
plt.show()