Alternating conditional expectations: Difference between revisions

Content deleted Content added
VZurko (talk | contribs)
VZurko (talk | contribs)
Line 13:
: <math> e^2(\theta,\varphi_1,\dots,\varphi_p)=\frac{\mathbb{E}\left[\theta(Y)-\sum_{i=1}^p \varphi_i(X_i)\right]^2}{\mathbb{E}[\theta^2(Y)]}</math>
Generally, the optimal transformations that minimize the unexplained part are difficult to compute directly. As an alternative, ACE is an iterative method to calculate the optimal transformations. The procedure of ACE has the following steps:
# Hold <math>\phi_1varphi_1(X_1),\dots,\phi_pvarphi_p(X_p)</math> fixed, minimizing <math>e^2</math><!--
-->gives <math>\theta_1(Y)=\mathbb{E}\left[\sum_{i=1}^p \varphi_i(X_i)\Bigg|Y\right]</math>
# Normalize <math>\theta_1(Y)</math> to unit variance.