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Introduction to the EM algorithm - Department of Statistics

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And finally in <strong>the</strong> same way using Lagrange multipliers and <strong>the</strong> restriction<br />

that ∑ M<br />

j=1 α j = 1 we have:<br />

ˆα j = 1 n<br />

n∑<br />

i=1<br />

p (k)<br />

ij<br />

.<br />

The updates are as follows:<br />

= ˆµ j<br />

σ 2 (k+1)<br />

j<br />

is ˆσ<br />

j 2 with µ j = µ (k+1)<br />

j<br />

;<br />

α (k+1)<br />

j<br />

= ˆα j .<br />

µ (k+1)<br />

j<br />

We iterate <strong>the</strong> E-step and M-step till convergence.<br />

Camila Souza (UBC) <strong>Introduction</strong> <strong>to</strong> <strong>the</strong> <strong>EM</strong> <strong>algorithm</strong> November 2010 22 / 25

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