File:Nonbayesian-gaussian-mixture.svg

\documentclass{article}
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%\usepackage{siunitx}
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\usepackage[graphics,tightpage,active]{preview}
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\usepackage{standalone}

\begin{document}

\begin{tikzpicture}
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  \node[param] (phi) [label=below:$\boldsymbol\phi$] {[K]};
  \node[main] (z) [right of=phi,label=below:$z_i$] {K};
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  \node[rectangle, inner sep=2mm, fit= (mu) (sigma),label=below right:K, yshift=-2mm, xshift=11mm] {};
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