Conditional Distribution

离散： $P(Y=y_j\mid X=x_i)=\frac{P(X=x_i,Y=y_j)}{P(X=x_i)}$

$P(Y=y\mid X=x)=\frac{P(X=x,Y=y)}{P_X(x)}$

连续：

$f_{Y\mid X}(y\mid x)=\frac{f_{X,Y}(x,y)}{f_X(x)}$