How to tell pgfplots to keep empty "series"?

Question

I have a plot with xticklabels defined as symbolic.

In a modified version of my plot, I want to set ymin value. When doing this, my plot is automatically updated: all x series having only points which y value is below this new ymin are removed. How can I change this behavior ?

Here is an example:

\documentclass[a4paper, landscape]{article}

\usepackage{pgfplots}
\usepackage[utf8]{inputenc}
\usepackage[margin=0.5cm]{geometry}

\pgfplotsset{compat=1.3}

\begin{document}

\centering
\begin{tikzpicture}
  \begin{axis}[
    symbolic x coords={X0, X1, X2, X3},
    xtick=data,
    grid=major,
    only marks
    ]
    \addplot coordinates {(X0,0) (X1,1) (X2,2) (X3,3)};
    \end{axis}
\end{tikzpicture}

\begin{tikzpicture}
  \begin{axis}[
    symbolic x coords={X0, X1, X2, X3},
    xtick=data,
    grid=major,
    only marks,
    ymin=1
    ]
    \addplot coordinates {(X0,0) (X1,1) (X2,2) (X3,3)};
    \end{axis}
\end{tikzpicture}

\end{document}

Here is the result. On the second graph I would like to have X0 xtick label visible even if it's point is not.

Answer 1

This doesn't seem to be clearly specified in the manual, but you can get the desired result by specifying xmin=X0 and enlarge x limits=true. Without the latter, X0 will lie on the y axis, i.e. there will no space to the left of X0:

\documentclass[a4paper, landscape]{article}

\usepackage{pgfplots}
\usepackage[utf8]{inputenc}
\usepackage[margin=0.5cm]{geometry}

\pgfplotsset{compat=1.3}

\begin{document}

\begin{tikzpicture}
  \begin{axis}[
    symbolic x coords={X0, X1, X2, X3},
    xtick=data,
    grid=major,
    only marks,
    ymin=1,
    xmin=X0,enlarge x limits=true
    ]
    \addplot coordinates {(X0,0) (X1,1) (X2,2) (X3,3)};
    \end{axis}
\end{tikzpicture}

\end{document}

In the general case you will also want to specify xmax to capture all your data points.