\documentclass[border = 3mmm]{standalone}
\usepackage{pgfplots}
\pgfplotsset{width=10cm,height=<<height>>cm,compat=newest}
\begin{document}
\begin{tikzpicture}
    \begin{axis}[
        % align left:
        legend style={
            cells={anchor=west},
            legend pos=outer north east,
            },
        xmin=<<min_val>>,
        xmax=<<max_val>>,
        % hide y axis,
        axis y line=none,
        axis x line=bottom,
        % set the precision of the x tick labels to be 0, which means no decimals
        % xticklabel style={/pgf/number format/precision=0},
        xtick={<<min_tval>>,...,<<max_tval>>},   %,<<min_tplus1>>
        axis x line shift={4pt},
        every outer x axis line/.append style={stealth-stealth},
        xlabel={<<xlabel>>}]
        \addplot [only marks, gray!40!, mark=*, mark size=3.5pt] coordinates{<<coords>>};
        \addplot [only marks, black, mark=*, mark size=1.2pt] coordinates{<<coords2>>};
        \legend{<<title>>, <<title2>>};
    \end{axis}
\end{tikzpicture}
\end{document}