$x$

$y$

+

$$f(x) \to y$$

$\hat{y}$

$x_1, x_2$$x_3, x_4$

$$p(x)$$

$\mathcal{C}_1 = \{x_1, x_3\}$

$\mathcal{C}_2 = \{x_2, x_4\}$

$x_1, x_2, x_3$

$x_1$

[ ]

$x_3$

$$P(x_2 \mid x_1, x_3)$$

$x_2$