import matplotlib.pyplot as plt
import numpy as np


def sigmoid(x, w=0, b=0):
    return 1 / (1 + (np.exp( - (w*x + b))))


# Experiment with different values of w
# The slope of the curve gets steep
########################################################################################################
for w in range(6, 100):

    x = np.linspace(-1, 1, 256)    
    
    y = []

    for each_x in x:
        y.append(sigmoid(each_x, w, b = 0))
    
    fig = plt.figure(figsize=(12, 10), dpi=100)
    
    ax = plt.subplot(111)
    ax.plot(x, y)

    # Hide the right and top spines
    ax.spines['right'].set_visible(False)
    ax.spines['top'].set_visible(False)
    
    plt.xlim(-1, 1)
    plt.ylim(0, 1)

    plt.plot(x, y, linewidth=2, color='red')
    
    start, end = ax.get_xlim()
    ax.xaxis.set_ticks(np.arange(start, end+.5, 0.5))
    
    ax.tick_params(direction="in")
    
    for tick in ax.xaxis.get_major_ticks():
        tick.label.set_fontsize(10) 
    
    plt.savefig('sig_2d/a_' + str(w) + '.jpg')
#     plt.show()


# Experiment with different values of b
# The curve shifts towards left
########################################################################################################

for b in range(1, 40):
    
    w = 50
    
    x = np.linspace(-1, 1, 256)    
    
    y = []

    for each_x in x:
        y.append(sigmoid(each_x, w, b))
    
    fig = plt.figure(figsize=(12, 10), dpi=100)
    
    ax = plt.subplot(111)
    ax.plot(x, y)

    # Hide the right and top spines
    ax.spines['right'].set_visible(False)
    ax.spines['top'].set_visible(False)
    
    plt.xlim(-1, 1)
    plt.ylim(0, 1)

    plt.plot(x, y, linewidth=2, color='red')
    
    start, end = ax.get_xlim()
    ax.xaxis.set_ticks(np.arange(start, end+.5, 0.5))
    
    ax.tick_params(direction="in")
    
    for tick in ax.xaxis.get_major_ticks():
        tick.label.set_fontsize(10) 
    
    plt.savefig('sig_2d/b_' + str(b) + '.jpg')
#     plt.show()