如何为 tikz 填充环境指定偏移节点引用？

Question

我在板图中有一些节点需要不同的背景颜色。理想情况下，整个图应该是彩色的：

梅威瑟：

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage{tikz}
\usetikzlibrary{bayesnet}

\begin{tikzpicture}

\pgfdeclarelayer{background}
\pgfsetlayers{background,main}

\node[obs]  (x)    {$x_i$};
\node[latent, above=15pt of x]  (z)   {$z_i$};
\node[latent, above left=5pt and 25pt of z] (pi)   {$\pi$};
\node[latent, below left=5pt and 25pt of x] (theta)  {$\theta$};

\edge{pi}{z};
\edge{theta}{x};
\edge{z}{x};

{\tikzset{plate caption/.append style={below right=1pt and 1pt of #1.south east}}
\plate[inner sep=0.35cm]{zwn}{(z)(x)}{\scriptsize{$10$}};}

\begin{pgfonlayer}{background}

% this needs to be something like "<10pt above left of pi> rectangle <50pt below right of z>"
\fill [orange!20] (pi) rectangle (z);

% this needs to be something like "<10pt below left of theta> rectangle <50pt above right of x>"
\fill [purple!20] (theta) rectangle (x);

\end{pgfonlayer}
\end{tikzpicture}

\end{document}

输出：

我想要的是：

Answer 1

欢迎！您可以使用节点锚点，并在需要时添加额外的班次。

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage{tikz}
\usetikzlibrary{bayesnet}
\begin{document}
\begin{tikzpicture}

\pgfdeclarelayer{background}
\pgfsetlayers{background,main}

\node[obs]  (x)    {$x_i$};
\node[latent, above=15pt of x]  (z)   {$z_i$};
\node[latent, above left=5pt and 25pt of z] (pi)   {$\pi$};
\node[latent, below left=5pt and 25pt of x] (theta)  {$\theta$};

\edge{pi}{z};
\edge{theta}{x};
\edge{z}{x};

\tikzset{plate caption/.append style={below right=1pt and 1pt of #1.south east}}
\plate[inner sep=0.35cm]{zwn}{(z)(x)}{\scriptsize{$10$}};

\begin{pgfonlayer}{background}

% this needs to be something like "<10pt above left of pi> rectangle <50pt below right of z>"
\fill [orange!20] ([xshift=-2ex,yshift=2ex]pi.north west) 
    rectangle ([xshift=1ex]zwn.east);

% this needs to be something like "<10pt below left of theta> rectangle <50pt above right of x>"
\fill [purple!20] ([xshift=-2ex,yshift=-2ex]theta.south west) 
    rectangle ([xshift=1ex]zwn.east);

\end{pgfonlayer}
\end{tikzpicture}
\end{document}