Data Science Fundamentals for Python and MongoDB by David Paper

Author:David Paper
Language: eng
Format: epub, pdf
Publisher: Apress, Berkeley, CA

def f(x):

return x**3 - 6 * x**2 + 9 * x + 15

def df(x):

return 3 * x**2 - 12 * x + 9

if __name__ == "__main__":

x = np.arange(-0.5, 5, 0.2)

y = f(x)

plt.figure('f(x)')

plt.xlabel('x')

plt.ylabel('f(x)')

plt.title('f(x)')

plt.plot(x, y, color="blueviolet")

plt.figure('local minimum')

plt.xlabel('x')

plt.ylabel('GD')

plt.title('local minimum')

iterations, cur_x, gamma, precision = 0, 6, 0.01, 0.00001

previous_step_size = cur_x

while previous_step_size > precision:

prev_x = cur_x

cur_x += -gamma * df(prev_x)

previous_step_size = abs(cur_x - prev_x)

iterations += 1

plt.plot(prev_x, cur_x, "o")

local_min = cur_x

print ('minimum:', local_min, 'iterations:', iterations)

plt.figure('local maximum')

plt.xlabel('x')

plt.ylabel('GD')

plt.title('local maximum')

iterations, cur_x, gamma, precision = 0, 0.5, 0.01, 0.00001

previous_step_size = cur_x

while previous_step_size > precision:

prev_x = cur_x

cur_x += -gamma * -df(prev_x)

previous_step_size = abs(cur_x - prev_x)

iterations += 1

plt.plot(prev_x, cur_x, "o")

local_max = cur_x

print ('maximum:', local_max, 'iterations:', iterations)

plt.show()

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