Why aren't empty ticks working with empty plots?

Question

I need to do an empty plot for my students to fill. Surprisingly the options xtick=\empty and ytick=\empty do not work when the plot is empty:

\documentclass{standalone}

\usepackage{pgfplots}
\pgfplotsset{compat=1.18}

\begin{document}
 
 \begin{tikzpicture}
 \begin{axis}[width=10cm, height=4cm, scale only axis,
  axis lines=center,
  xtick=\empty, ytick=\empty,
  xlabel=$x$, ylabel=$f$]
%   \addplot {x+1};
 \end{axis}
\end{tikzpicture}
 
\end{document}

I have been able to achieve my ends with the option ticks=none as explained here, but this is not totally satisfactory since this workaround does not allow to cancel ticks on a single axis if needed. Besides I was not able to find this option in the Pgfplots documentation.

Why the \empty command does not work here?

Answer 1

It happens because the range of coordinates calculates according to its content. When it's missing I believe, pgfplots just draws default axis, ignoring most options (notice that axis lines=center doesn't work either).

You have three options:

1. Disable ticks with ticks=none as you described. If you want to eliminate only x ticks or y ticks, you can set xmajorticks=false or xmajorticks=false similarly

   

   \documentclass{article}
   
   \usepackage{pgfplots}
   \pgfplotsset{compat=newest}
   
   \begin{document}
   
    \begin{tikzpicture}
    \begin{axis}[width=10cm, height=4cm, scale only axis,
     axis lines=center,
     xlabel=$x$, ylabel=$f$,
     xmajorticks=false
     ]
    \end{axis}
   
    \end{tikzpicture}
   
   \end{document}
   

2. Put something invisible via \addplot so the data of axis isn't blank

   

   \documentclass{article}
   
   \usepackage{pgfplots}
   \pgfplotsset{compat=newest}
   
   \begin{document}
   
    \begin{tikzpicture}
    \begin{axis}[width=10cm, height=4cm, scale only axis,
     axis lines=center,
     xtick=\empty, ytick=\empty,
     xlabel=$x$, ylabel=$f$,
     ]
      \addplot[draw=none]{0};
    \end{axis}
   
    \end{tikzpicture}
   
   \end{document}
   

3. And the most correct was is to specify all xmin, xmax, ymin, ymax so the axis doesn't rely on content anymore, but the values you set, thus \empty works.

   \documentclass{article}
   
   \usepackage{pgfplots}
   \pgfplotsset{compat=newest}
   
   \begin{document}
   
    \begin{tikzpicture}
    \begin{axis}[width=10cm, height=4cm, scale only axis,
     axis lines=center,
     xtick=\empty, ytick=\empty,
     xlabel=$x$, ylabel=$f$,
     xmin=-1, xmax=5,
     ymin=-3, ymax=2
     ]
    \end{axis}
   
    \end{tikzpicture}
   
   \end{document}