Vertical alignment in TikZ matrix

Question

I am using a TikZ matrix to make a diagram where the entries in a row vary considerably in size:

\documentclass{article}

\usepackage{tikz,amsmath}
\usetikzlibrary{matrix}

\begin{document}

\newcommand{\RandomDots}{%
    \begin{tikzpicture}
        \foreach \x in {0.1, 0.3,...,1}
            \foreach \y in {0.1, 0.3,...,1}
            {
                \pgfmathrandominteger{\r}{1}{5}
                \fill (\x,\y) circle [radius=\r/5 pt];
            }
    \end{tikzpicture}
}

\begin{tikzpicture}[%
    feature box/.style = {rectangle, draw, anchor=center},
    ]

    \matrix [
        matrix of math nodes,
        column sep = 1cm,
        row sep = 0.1cm
    ]
    {
        |(a)| a & \node [feature box] (f1) {\RandomDots}; \\
        |(b)| b & \node [feature box] (f2) {\RandomDots}; \\
    };

    \draw [->] (a) -- (f1);
    \draw [->] (b) -- (f2);
\end{tikzpicture}
\end{document}

The resulting image looks like this:

However, I would like the connections to be horizontal/the box from \RandomDots to be vertically aligned with the letters in the first column.

Does anyone know of a way to do this?

Answer 1

try

\draw [->] (a) -- (f1.west|-a);

\draw [->] (b) -- (f2.west|-b);