# How can I draw a full circle at the origin when I have the y-axis to the left and the x-axis in the bottom?

I am trying to draw a circular node at the origin,while keeping the y-axis to the left and the x-axis to the bottom. The node results to be a quarter of a circle. How can I keep it full circle while preserving the axis?

Below is the code I am using.

\begin{tikzpicture}[baseline]
\begin{axis}[
axis y line = left,
axis x line=bottom,
xlabel = t,
xtick = {\empty},
ytick =  {\empty},
]
domain=-6:6,
samples=100,
color=gray,
line width = 0.55mm,
]
{1/(1+exp(-\x))};
\end{axis} ;

\end{tikzpicture}
}


Thank you!

• You can draw it outside the axis environment, if you first create a named coordinate at (axis cs: 0,0). Oct 11, 2016 at 22:55

One possibility is

after end axis/.code={\draw[fill] (current axis.origin) circle[radius=3pt];}


to avoid that the node is clipped at the border of the axis. Instead (current axis.origin) you could also use (axis cs:0,0) in the code above.

\documentclass[margin=5pt]{standalone}
\usepackage{pgfplots}
\begin{document}
\begin{tikzpicture}[baseline]
\begin{axis}[
axis y line = left,
axis x line=bottom,
xlabel = t,
xtick = {\empty},
ytick =  {\empty},
after end axis/.code={\draw[fill] (current axis.origin) circle[radius=3pt];}
]
domain=-6:6,
samples=100,
color=gray,
line width = 0.55mm
]
{1/(1+exp(-\x))};
\end{axis}
\end{tikzpicture}
\end{document}


I'd use

\addplot[color=black,only marks,mark=*] (-6,0);


which gives

here's a complete MWE:

% arara: pdflatex
\documentclass{standalone}
\usepackage{pgfplots}

\begin{document}

\begin{tikzpicture}
\begin{axis}[
axis y line = left,
axis x line=bottom,
xlabel = t,
xtick = {\empty},
ytick =  {\empty},
]
domain=-6:6,
samples=100,
color=gray,
line width = 0.55mm,
]
{1/(1+exp(-\x))};