# How to draw a hysteresis loop with TikZ datavisualization?

Sorry for my incorrect english.

I have modified the code from here to adapt it for the TikZ datavisualization. Here is the adapted code:

\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}


But I get many of this errors:

! Dimension too large. \pgfmath@iterate ...\pgfmath@xa \ifdim \pgfmath@x

One can use the TikZ fpu like did here, here and here. Here is my code:

\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}


But than my pdfLaTeX compiler of TeXnicCenter runs into an endless loop. What do I wrong?

By the way: The decoration lines above looks already the same (only coordinates, alignment and text changes). Is there a way to combine/optimize it.

Seems that when the x-value becomes a "large" negative number, it breaks down. If you change the lower limit of the left curve to -6.5, and for the right curve to -4.5, it compiles fine here.

\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}

• Hello @Torbjørn T.! Sorry for the long absence. Thank you for the answer. But I search for a general solution (for example fpu). Because if I change slightly the functions, it is enough to change the factor of x (for example if I wish to compare two hysteresis loops on one coordinate system) than I have the same problem as before. What do you say? – Su-47 Jan 28 '17 at 15:25
• @Su-47 I don't really have anything to say, I'm afraid. I don't have a general solution. – Torbjørn T. Jan 28 '17 at 18:02
• Hello @Torbjørn T.! Thank you for your comment. No problem! Maybe someone has a solution? – Su-47 Jan 29 '17 at 6:25
• Hello everybody! Since the question couldn't be answered in general. I try to ask a similar question. Maybe then I have more luck. – Su-47 Feb 15 '17 at 20:01
• Forgot the link. – Su-47 Feb 15 '17 at 20:17