<SYSTEM_TASK:>
Given the following text description, write Python code to implement the functionality described below step by step
<END_TASK>
<USER_TASK:>
Description:
 活性化関数
ステップ関数
$y=\begin{cases}1 & ( x \gt 0 ) \-1 & ( x \leqq 0 )\end{cases}$
Step1:  シグモイド関数
$y = \frac{1}{1 + exp(-x)}$
Step2:  ReLU関数
$y=\begin{cases}x & ( x \gt 0 ) \ 0 & ( x \leqq 0 ) \end{cases}$
<ASSISTANT_TASK:>
Python Code:
x = np.arange(-5.0, 5.0, 0.1)
y = np.array(x > 0, dtype=np.int)
plt.plot(x, y)
plt.show()
Explanation: 活性化関数
ステップ関数
$y=\begin{cases}1 & ( x \gt 0 ) \-1 & ( x \leqq 0 )\end{cases}$
End of explanation
x = np.arange(-5.0, 5.0, 0.1)
y = 1 / (1 + np.exp(-x))
plt.plot(x, y)
plt.show()
Explanation: シグモイド関数
$y = \frac{1}{1 + exp(-x)}$
End of explanation
x = np.arange(-5.0, 5.0, 0.1)
y = np.maximum(0, x)
plt.plot(x, y)
plt.show()
Explanation: ReLU関数
$y=\begin{cases}x & ( x \gt 0 ) \ 0 & ( x \leqq 0 ) \end{cases}$
End of explanation
<END_TASK>