Problem with tikz : alignment of figure when using bracket in xlabel

Question

When I put bracket in a xlabel, the alignement of my figure change. It's just a little move, but it's uggly because i put two sub figures side by side.

Do you know how to solve this ?

Thanks in advance,

Thomas

PS : I think Here : TikZ graph not aligning is the same problem, but unresolved.

\documentclass[10pt]{article}

\usepackage{pgfplots}
\usepackage{subcaption}

\begin{document}

\begin{figure}
\centering
\begin{subfigure}[b]{0.45 \textwidth}
\caption{sub-figure 1}
\begin{tikzpicture}
\tikzstyle{every node}=[font=\small]
\begin{axis}[height=\textwidth,width=\textwidth,
axis lines=left, enlarge x limits=true, enlarge y limits=true,
xlabel={x},
scaled x ticks = false,
ylabel={y},
x tick label style={/pgf/number format/fixed, /pgf/number format/1000 sep = \thinspace},
]
\addplot[ybar,ybar interval=0] coordinates{
(0,8) (500,87) (1000,127) (1500,93) (2000,68) (2500,51) (3000,40) (3500,17) (4000,19) (4500,14) (5000,11)                   (5500,2) (6000,1) (6500,1) (7000,0)};
\end{axis}
\end{tikzpicture}
\end{subfigure}
~
\begin{subfigure}[b]{0.45 \textwidth}
\caption{sub-figure 2}
\begin{tikzpicture}
\tikzstyle{every node}=[font=\small]
\begin{axis}[height=\textwidth,width=\textwidth,
axis lines=left, enlarge x limits=true, enlarge y limits=true,
xlabel={x {(test)}},
scaled x ticks = false,
ylabel={x},
x tick label style={/pgf/number format/fixed, /pgf/number format/1000 sep = \thinspace},
]
\addplot[ybar,ybar interval=0] coordinates{
(0,8) (500,87) (1000,127) (1500,93) (2000,68) (2500,51) (3000,40) (3500,17) (4000,19) (4500,14) (5000,11)                   (5500,2) (6000,1) (6500,1) (7000,0)};
\end{axis}
\end{tikzpicture}   
\end{subfigure} 
\end{figure}
\vfill
\end{document}

Answer 1

There are several ways to fix this:

1. As per Zarko's comment you can add a xlabel={$x$ \vphantom{(test)}}. The reason is the initial mismatch was the additional height of the (. Adding a \vphantom ensures that the both labels are of the same height. You actually on need a \vphantom{(}, but in other cases you may need the full text of the other label.

2. Add a strut as in xlabel={$x$\strut}. The \strut should be added to both of the labels.

3. Specify a style for the xlabel which positions the label correctly (as in the MWE below).

   

Notes:

• Axis labels should probably be in math mode as per the MWE below.

Code:

\documentclass[10pt]{article}

\usepackage{pgfplots}
\usepackage{subcaption}

\pgfplotsset{compat=1.11}

\begin{document}

\begin{figure}
\centering
\begin{subfigure}[b]{0.45 \textwidth}
\caption{sub-figure 1}
\begin{tikzpicture}
\tikzstyle{every node}=[font=\small]
\begin{axis}[height=\textwidth,width=\textwidth,
axis lines=left, enlarge x limits=true, enlarge y limits=true,
xlabel={$x$},
scaled x ticks = false,
ylabel={$y$},
x tick label style={/pgf/number format/fixed, /pgf/number format/1000 sep = \thinspace},
xlabel style={at={(0.5,0)}, below,yshift=-25pt, anchor=base, inner sep=0pt, minimum height=2.0ex}
]
\addplot[ybar,ybar interval=0] coordinates{
(0,8) (500,87) (1000,127) (1500,93) (2000,68) (2500,51) (3000,40) (3500,17) (4000,19) (4500,14) (5000,11)                   (5500,2) (6000,1) (6500,1) (7000,0)};
\end{axis}
\end{tikzpicture}
\end{subfigure}
~
\begin{subfigure}[b]{0.45 \textwidth}
\caption{sub-figure 2}
\begin{tikzpicture}
\tikzstyle{every node}=[font=\small]
\begin{axis}[height=\textwidth,width=\textwidth,
axis lines=left, enlarge x limits=true, enlarge y limits=true,
xlabel={$x$ (test)},
scaled x ticks = false,
ylabel={$x$},
x tick label style={/pgf/number format/fixed, /pgf/number format/1000 sep = \thinspace},
xlabel style={at={(0.5,0)}, below,yshift=-25pt, anchor=base, inner sep=0pt, minimum height=2.0ex}
]
\addplot[ybar,ybar interval=0] coordinates{
(0,8) (500,87) (1000,127) (1500,93) (2000,68) (2500,51) (3000,40) (3500,17) (4000,19) (4500,14) (5000,11)                   (5500,2) (6000,1) (6500,1) (7000,0)};
\end{axis}
\end{tikzpicture}   
\end{subfigure} 
\end{figure}
\vfill
\end{document}

Answer 2

A label generally fit on one line. So you can set the height and depth of the text for all axis labels:

\pgfplotsset{
  compat=1.11,
  label style={text height=.8em,text depth=.15em},
}

With this style, your figures are correctly aligned (horizontally and vertically) and labels use the same baseline.

Your MWE, completed:

\documentclass[10pt]{article}

\usepackage{pgfplots}
\usepackage{subcaption}

\pgfplotsset{
  compat=1.11,
  label style={text height=.8em,text depth=.15em},
}

\begin{document}
\begin{figure}
  \centering
  \begin{subfigure}[b]{0.45 \textwidth}
    \caption{sub-figure 1}
    \begin{tikzpicture}
      \tikzstyle{every node}=[font=\small]
      \begin{axis}[height=\textwidth,width=\textwidth,
        axis lines=left, enlarge x limits=true, enlarge y limits=true,
        xlabel={x},
        scaled x ticks = false,
        ylabel={y},
        x tick label style={/pgf/number format/fixed, /pgf/number format/1000 sep = \thinspace},
        ]
        \addplot[ybar,ybar interval=0] coordinates{
          (0,8) (500,87) (1000,127) (1500,93) (2000,68) (2500,51) (3000,40) (3500,17) (4000,19) (4500,14) (5000,11)                   (5500,2) (6000,1) (6500,1) (7000,0)};
      \end{axis}
    \end{tikzpicture}
  \end{subfigure}
  ~
  \begin{subfigure}[b]{0.45 \textwidth}
    \caption{sub-figure 2}
    \begin{tikzpicture}
      \tikzstyle{every node}=[font=\small]
      \begin{axis}[height=\textwidth,width=\textwidth,
        axis lines=left, enlarge x limits=true, enlarge y limits=true,
        xlabel={x {(test)}},
        scaled x ticks = false,
        ylabel={x},
        x tick label style={/pgf/number format/fixed, /pgf/number format/1000 sep = \thinspace},
        ]
        \addplot[ybar,ybar interval=0] coordinates{
          (0,8) (500,87) (1000,127) (1500,93) (2000,68) (2500,51) (3000,40) (3500,17) (4000,19) (4500,14) (5000,11)                   (5500,2) (6000,1) (6500,1) (7000,0)};
      \end{axis}
    \end{tikzpicture}   
  \end{subfigure} 
\end{figure}
\vfill
\end{document}