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如何获取 tikz 中文本/数学节点的适当高度？

tag-icon • tag-icon tikz-pgf
如何获取 tikz 中文本/数学节点的适当高度？

我有以下卡尔曼滤波器的框图：

在此处输入图片描述

我认为框的上边框和第一行数学之间的间距太大。我该如何减少间距以使其看起来更美观？

代码

\documentclass[varwidth=true, border=2pt]{standalone}

\usepackage{pgfplots}
\usepackage{tikz}
\usetikzlibrary{shapes,arrows}
\pgfplotsset{compat=1.13}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{xcolor}

\begin{document}
\tikzstyle{block} = [draw, rectangle, minimum width=6em, align=center]
\newcommand*{\tran}{\top}

\begin{tikzpicture}[auto, node distance=2cm,>=latex']
    % Place the blocks
    \node[text width=1cm, draw,
          rounded corners=3pt,
          label={[above,align=center]{Initial\\State}}] at (-1, 0) (initial)
          {$$\mathbf{x}_0$$  $$P_0$$};
    \node at (0.25, 0) (sum) {};
    \node[block, text width=6cm,
          label={[above,align=center]{Prediction}}] at (4, 0) (prediction)
          {\begin{align*}
            \mathbf{x}_{k+1}^{(P)} &= A x_k + B {\color{orange} a_k}\\
            P_{k+1}^{(P)} &= A P_k A^\tran + C_k^{(r_s)}
           \end{align*}};
    \node [block, right of=prediction,
            node distance=3cm, text width=1cm] at (6, -2) (iterUpdate)
            {$$k \leftarrow k + 1$$};
    \node [block, text width=6cm,
           label={[above,align=center]{Innovation}}] at (4, -4) (innovation)
           {\begin{align*}
              K_k &= P_k^{(P)} H^\tran {(H P_k^{(P)} H^\tran + C_k^{(M)})}^{-1}\\
              {\color{blue} x_k} &= \mathbf{x}_k^{(P)} + K_k \left ({\color{orange} z_k} - H \mathbf{x}_k^{(P)} \right )\\
              {\color{blue} P_k} &= (I - K_k H) P_k^{(P)}
            \end{align*}};

    % Connect the nodes
    \draw [->] (initial) -- (prediction);
    \draw [->] (prediction.east) -| (iterUpdate.north);
    \draw [->] (iterUpdate) |- (innovation);
    \draw [->] (innovation.west) -|  (sum);
\end{tikzpicture}

\end{document}

答案1

您只需在代码中添加一行即可做到这一点\setlength{\abovedisplayskip}{0pt}，该行控制处于显示模式（非文本模式）的方程式上方的空间

输出

在此处输入图片描述

代码

\documentclass[varwidth=true, border=2pt]{standalone}

\usepackage{pgfplots}
\usepackage{tikz}
\usetikzlibrary{shapes,arrows}
\pgfplotsset{compat=1.13}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{xcolor}

\begin{document}
\tikzstyle{block} = [draw, rectangle, minimum width=6em, align=center]
\newcommand*{\tran}{\top}

\begin{tikzpicture}[auto, node distance=2cm,>=latex']
\setlength{\abovedisplayskip}{0pt}
    % Place the blocks
    \node[text width=1cm, draw,
          rounded corners=3pt,
          label={[above,align=center]{Initial\\State}}] at (-1, 0) (initial)
          {$$\mathbf{x}_0$$  $$P_0$$};
    \node at (0.25, 0) (sum) {};
    \node[block, text width=6cm,
          label={[above,align=center]{Prediction}}] at (4, 0) (prediction)
          {\begin{align*}
            \mathbf{x}_{k+1}^{(P)} &= A x_k + B {\color{orange} a_k}\\
            P_{k+1}^{(P)} &= A P_k A^\tran + C_k^{(r_s)}
           \end{align*}};
    \node [block, right of=prediction,
            node distance=3cm, text width=1cm] at (6, -2) (iterUpdate)
            {$$k \leftarrow k + 1$$};
    \node [block, text width=6cm,
           label={[above,align=center]{Innovation}}] at (4, -4) (innovation)
           {\begin{align*}
              K_k &= P_k^{(P)} H^\tran {(H P_k^{(P)} H^\tran + C_k^{(M)})}^{-1}\\
              {\color{blue} x_k} &= \mathbf{x}_k^{(P)} + K_k \left ({\color{orange} z_k} - H \mathbf{x}_k^{(P)} \right )\\
              {\color{blue} P_k} &= (I - K_k H) P_k^{(P)}
            \end{align*}};

    % Connect the nodes
    \draw [->] (initial) -- (prediction);
    \draw [->] (prediction.east) -| (iterUpdate.north);
    \draw [->] (iterUpdate) |- (innovation);
    \draw [->] (innovation.west) -|  (sum);
\end{tikzpicture}

\end{document}

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