Aligning an array with text beside it

Question

I am trying to create a 'matrix' using the array environment. I have multiple of these lines each with text besides it of varying length. I would like to have the array aligned; however, in example below, the differing length of text changes that alignment

\documentclass{article}
\usepackage{gensymb}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{dcolumn}
\newcolumntype{R}{D{.}{.}{2,6}}
\begin{document}
\[
\left[
    \begin{array}{@{}RR|R@{}}
        0.28 &0.72 &45\\
        0.72 &0.28 &55\\
    \end{array}
\right]
test
\]
\[
\left[
    \begin{array}{@{}RR|R@{}}
        0.28 &0.72 &45\\
        0.2016 &0.0784 &15.4\\
    \end{array}
\right]
test1
\]
\[
\left[
    \begin{array}{@{}RR|R@{}}
        0.2016 &0.5184 &32.4\\
        0.2016 &0.0784 &15.4\\
    \end{array}
\right]
test12
\]
\end{document}

I have tried using /hfill and the align/* environment with no success; however, my knowledge of latex is extremely limited.

Answer 1

I'd use aligned (and siunitx rather than dcolumn)

\documentclass{article}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{siunitx}
\newcolumntype{R}[1]{S[table-format=#1]}

\begin{document}
\[
\begin{aligned}
\left[
    \begin{array}{@{}R{2.4}R{2.4}|R{2.1}@{}}
        0.28 &0.72 &45\\
        0.72 &0.28 &55\\
    \end{array}
\right]
&\quad\text{test}
\\
\left[
    \begin{array}{@{}R{2.4}R{2.4}|R{2.1}@{}}
        0.28 &0.72 &45\\
        0.2016 &0.0784 &15.4\\
    \end{array}
\right]
&\quad\text{test1}
\\
\left[
    \begin{array}{@{}R{2.4}R{2.4}|R{2.1}@{}}
        0.2016 &0.5184 &32.4\\
        0.2016 &0.0784 &15.4\\
    \end{array}
\right]
&\quad\text{test12}
\end{aligned}
\]

\end{document}

Answer 2

You could place the right-hand text material into a fixed-width \parbox:

The fixed width chosen in the code below is 2cm; you're obviously free to adapt this width to your typesetting needs. Note also that the contents of a \parbox are typeset in text mode by default; this is true even if the \parbox occurs inside math mode.

\documentclass{article}
\usepackage{gensymb}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{dcolumn}
\newcolumntype{R}{D{.}{.}{2,6}}
\begin{document}
\[
\left[
    \begin{array}{@{}RR|R@{}}
        0.28 &0.72 &45\\
        0.72 &0.28 &55\\
    \end{array}
\right]
\parbox{2cm}{test}
\]
\[
\left[
    \begin{array}{@{}RR|R@{}}
        0.28   &0.72   &45\\
        0.2016 &0.0784 &15.4\\
    \end{array}
\right]
\parbox{2cm}{test1}
\]
\[
\left[
    \begin{array}{@{}RR|R@{}}
        0.2016 &0.5184 &32.4\\
        0.2016 &0.0784 &15.4\\
    \end{array}
\right]
\parbox{2cm}{test12}
\]
\end{document}