Complex matrices column alignment on sign

Question

Background:

I would like to improve my matlab function mat2lat(A):

https://github.com/KasparJohannesSchneider/mat2lat/issues/1

Problem:

For complex matrices, the alignment mode {c} doesn't look very good because the + and - signs in between the real and the imaginary part are not aligned, see screenshot below. Because the LaTex code is created programmatically, it wouldn't be a problem to just create a separate column for the sign, however, this results in a weird-looking space to the left and right of this column, see "Ugly workaround" below.

Question:

First of all, I would strongly prefer not to include any packages other than \usepackage{amsmath}. What is the best solution for displaying complex matrices in LaTex?

Minimal Working Example:

\documentclass[11pt, titlepage, oneside, a4paper]{article}
\usepackage{amsmath}

\begin{document}

    \textbf{Works for real matrices:}
    $$\left[\begin{array}{ccc}
        {64+2.828i} & {1+1i}      & {36+2.449i} \\
        {9+1.732i}  & {25+2.236i} & {49+2.646i} \\
        {16+2i}     & {81+3i}     & {4+1.414i} 
    \end{array}\right]$$

    \textbf{Ugly workaround:}
    $$\left[\begin{array}{rclcrclcrcl}
        64&+&2.828i && 1&+&1i      && 36&+&2.449i \\
        9&+&1.732i  && 25&+&2.236i && 49&+&2.646i \\
        16&+&2i     && 81&+&3i     && 4&+&1.414i 
    \end{array}\right]$$
\end{document}

Answer 1

If no further packages can be loaded you have to add the correct \medmuskip around the binary operators by hand

\documentclass{article}

\usepackage{amsmath}

\begin{document}

\[ % never use $$...$$ in LaTeX: https://tex.stackexchange.com/q/503/82917
\left[
\begin{array}{*{3}{r@{\mskip\medmuskip}c@{\mskip\medmuskip}l}}
64&+&2.828i & 1&+&1i      & 36&+&2.449i \\
9&+&1.732i  & 25&+&2.236i & 49&+&2.646i \\
16&+&2i     & 81&+&3i     & 4&+&1.414i 
\end{array}
\right]
\]

\end{document}

Answer 2

Why not simply three aligned environments inside a \bmatrix?

Unrelated: for displayed equations, use the latex construct \[ ... \], note plain TeX $$ ... $$.

\documentclass[11pt, titlepage, oneside, a4paper]{article}
\usepackage{amsmath}
\begin{document}
[ \begin{bmatrix}
      , \begin{aligned}
         64&+2.828i \ 9&+1.732i \ 16&+2i
       \end{aligned}
      & \begin{aligned}
       1&+1i \ 25&+2.236i \ 81&+3i
       \end{aligned}
       & \begin{aligned}
       36&+ 2.449i \ 49&+ 2.646i \ 4 & + 1.414i
       \end{aligned},
    \end{bmatrix} ]
\end{document} 

Answer 3

If you're willing to work with some other packages, you can capture the argument of every cell in a newly-defined column (say) I and then process (separating out the real/imaginary parts):

\documentclass{article}

\usepackage{amsmath,eqparbox,collcell,etoolbox}

\newcolumntype{I}{>{\collectcell\RpmI}c<{\endcollectcell}}
\makeatletter
\def\rplusi@#1+#2\relax{% R + Ii
  \eqmakebox[R][r]{$#1$} + \eqmakebox[I][l]{$#2$}%
}
\def\rminusi@#1-#2\relax{% R - Ii
  \eqmakebox[R][r]{$#1$} - \eqmakebox[I][l]{$#2$}%
}
\newcommand{\RpmI}[1]{%
  \def\abc{#1}% Store argument R +/- Ii
  \patchcmd{\abc}{+}{+}{%
    \expandafter\rplusi@#1\relax% R + Ii
  }{%
    \expandafter\rminusi@#1\relax% R - Ii
  }%
}
\makeatother

\begin{document}

\textbf{Works for real matrices:}
\[
  \left[\begin{array}{ccc}
    64 - 2.828i &  1 + 1i     & 36 - 2.449i \\
     9 + 1.732i & 25 - 2.236i & 49 + 2.646i \\
    16 - 2i     & 81 + 3i     &  4 - 1.414i
  \end{array}\right]
\]

\textbf{Workaround:}
\[
  \left[\begin{array}{III}
    64 - 2.828i &  1 + 1i     & 36 - 2.449i \\
     9 + 1.732i & 25 - 2.236i & 49 + 2.646i \\
    16 - 2i     & 81 + 3i     &  4 - 1.414i
  \end{array}\right]
\]

\end{document}