如何使用 TikZ 数据可视化绘制磁滞回线？

Question

抱歉我的英语不正确。

我修改了代码这里以适应TikZ datavisualization。以下是改编后的代码：

\documentclass{scrartcl}
\usepackage{tikz}
\usepackage[per-mode = fraction]{siunitx}
\usetikzlibrary{datavisualization.formats.functions}
\begin{document}
  \begin{tikzpicture}
    \datavisualization[
                       scientific axes = {clean, end labels},
                       all axes = {ticks and grid = {major at = 0}},
                       x axis = {label = $\frac{H}{\si{\A\per\m}}$},
                       y axis = {label = $\frac{B(H)}{\si{\tesla}}$},
                       data/format = function,
                       visualize as smooth line/.list = {left, right}
                      ]
    data[set = left] {
      var x : interval [-7 : 7];
      func y = 5 / (1 + exp(-1.7 * \value x - 1.5)) - 2.5;
    }
    data[set = right] {
      var x : interval [-7 : 7];
      func y = 5 / (1 + exp(-1.7 * \value x + 1.5)) - 2.5;
    }
    %accents important points
    info {
      \draw (visualization cs:x = {(-1.5 / 1.7)}, y = 0) circle [radius = 1pt]
        node [left, font = \footnotesize] {$H_C$};
    }
    info {
      \draw (visualization cs:x = 0, y = 1.59) circle [radius = 1pt]
        node [left, font=\footnotesize] {$B_R$};
    }
    info {
      \draw (visualization cs:x = 7, y = 2.5) circle [radius = 1pt]
        node [above, font=\footnotesize] {$B_S$};
    };
  \end{tikzpicture}
\end{document}

但我遇到了许多这样的错误：

！尺寸太大 \pgfmath@iterate。...\pgfmath@xa \ifdim \pgfmath@x

你也可以使用TikZ fpu类似这里，这里和这里。这是我的代码：

\documentclass{scrartcl}
\usepackage{tikz}
\usepackage[per-mode = fraction]{siunitx}
\usetikzlibrary{datavisualization.formats.functions,fpu}
\begin{document}
  \begin{tikzpicture}
    \datavisualization[
                       scientific axes = {clean, end labels},
                       all axes = {ticks and grid = {major at = 0}},
                       x axis = {label = $\frac{H}{\si{\A\per\m}}$},
                       y axis = {label = $\frac{B(H)}{\si{\tesla}}$},
                       data/format = function,
                       visualize as smooth line/.list = {left, right}
                      ]
    data[set = left] {
      var x : interval [-7 : 7];
      \pgfkey{/pgf/fpu, /pgf/fpu/output format=fixed}
      func y = 5 / (1 + exp(-1.7 * \value x - 1.5)) - 2.5;
      \pgfkeys{/pgf/fpu=false}
    }
    data[set = right] {
      var x : interval [-7 : 7];
      \pgfkey{/pgf/fpu, /pgf/fpu/output format=fixed}
      func y = 5 / (1 + exp(-1.7 * \value x + 1.5)) - 2.5;
      \pgfkeys{/pgf/fpu=false}
    }
    %accents important points
    info {
      \draw (visualization cs:x = {(-1.5 / 1.7)}, y = 0) circle [radius = 1pt]
        node [left, font = \footnotesize] {$H_C$};
    }
    info {
      \draw (visualization cs:x = 0, y = 1.59) circle [radius = 1pt]
        node [left, font=\footnotesize] {$B_R$};
    }
    info {
      \draw (visualization cs:x = 7, y = 2.5) circle [radius = 1pt]
        node [above, font=\footnotesize] {$B_S$};
    };
  \end{tikzpicture}
\end{document}

但是我的pdfLaTeX编译器TeXnicCenter陷入了无限循环。我哪里做错了？

顺便说一句：上面的装饰线看起来已经一样了（只有坐标、对齐和文本变化）。有没有办法合并/优化它。

提前谢谢你的帮助！

Answer 1

似乎当 x 值变成“大”负数时，它就会崩溃。如果将曲线的下限更改left为 -6.5，并将right曲线更改为 -4.5，则在此处编译正常。

\documentclass{scrartcl}
\usepackage{tikz}
\usepackage[per-mode = fraction]{siunitx}
\usetikzlibrary{datavisualization.formats.functions}
\begin{document}
  \begin{tikzpicture}
    \datavisualization[
                       scientific axes = {clean, end labels},
                       all axes = {ticks and grid = {major at = 0}},
                       x axis = {label = $\frac{H}{\si{\A\per\m}}$},
                       y axis = {label = $\frac{B(H)}{\si{\tesla}}$},
                       data/format = function,
                       visualize as smooth line/.list = {left, right}
                      ]
    data[set = left] {
      var x : interval [-6.5 : 7];
      func y = 5 / (1 + exp(-1.7 * \value x - 1.5)) - 2.5;
    }
    data[set = right] {
      var x : interval [-4.5 : 7];
      func y = 5 / (1 + exp(-1.7 * \value x + 1.5)) - 2.5;
    }
    %accents important points
    info {
      \draw (visualization cs:x = {(-1.5 / 1.7)}, y = 0) circle [radius = 1pt]
        node [left, font = \footnotesize] {$H_C$};
    }
    info {
      \draw (visualization cs:x = 0, y = 1.59) circle [radius = 1pt]
        node [left, font=\footnotesize] {$B_R$};
    }
    info {
      \draw (visualization cs:x = 7, y = 2.5) circle [radius = 1pt]
        node [above, font=\footnotesize] {$B_S$};
    };
  \end{tikzpicture}
\end{document}