align elements of matrix with a bmatrix inside

Question

I have made the following matrix:

\newcommand{\mtx}[2]{\begin{#1matrix}#2\end{#1matrix}}
\newcommand{\mtxR}[2]{\begin{#1matrix*}[r]#2\end{#1matrix*}}
\begin{equation*}
    A=\mtx{}{\mtx{}{e_1&e_2&e_3&e_4&e_5&e_6&e_7&e_8}&\\\mtxR{b}{1&&1&&&&&\\-1&1&&1&&&&\\&-1&&&1&1&&\\&&&&-1&-1&&1\\&&&-1&&&1&-1\\&&-1&&&&-1&}&\mtx{}{v_1\\v_2\\v_3\\v_4\\v_5\\v_6}}
\end{equation*}

Is there a way to align the e's in the top row with the numbers in the bmatrix, and the same for the v's in the most right column?

Answer 1

Like this?

\documentclass{article}
\usepackage{blkarray}
\begin{document}

\[
A=\begin{blockarray}{cccccc}
e_1 & e_2 & e_3 & e_4 & e_5 \\
\begin{block}{[ccccc]l}
  1 & -1 & 1 & 1 & 1 & v_1 \\
    & 1  &   &   & 1 & v_2 \\
    &    & 1 &   & 1 & v_3 \\
    &    &   & 1 & 1 & v_4 \\
    &    &   &   & 1 & v_5 \\
\end{block}
\end{blockarray}
\]
\end{document}

If you wanted the 1 and the -1 entries to line up so that the numerals were exactly under each other, you could try defining the inner block with [rrrrr]l. But you might think (for example) that the right hand column was too close to the right bracket.

Or you can "cheat" with \smash to set the minus signs in zero-width boxes. Personally I don't mind the -1 entries sticking out to the right a bit, as I think it might make them easier to read.

Or you can use nicematrix as the other answer shows.

Answer 2

You can use nicematrix.

\documentclass{article}
\usepackage{nicematrix}

\begin{document}
\[
\begin{bNiceArray}{*{8}{R}}[
  first-row,
  last-col,
]
e_1 & e_2 & e_3 & e_4 & e_5 & e_6 & e_7 & e_8 & \\
  1 &     &   1 &     &     &     &     &     & v_1 \\
 -1 &   1 &     &   1 &     &     &     &     & v_2 \\
    &  -1 &     &     &   1 &   1 &     &     & v_3 \\
    &     &     &     &  -1 &  -1 &     &   1 & v_4 \\
    &     &     &  -1 &     &     &   1 &  -1 & v_5 \\
    &     &  -1 &     &     &     &  -1 &     & v_6 \\
\end{bNiceArray}
\]

\end{document}

Answer 3

Here are two ways: with blkarray and with bigdelim:

\documentclass{article}
\usepackage{array, blkarray}
\usepackage{bigdelim} 

\begin{document}

\[ A = \begin{blockarray}{*{8}{r}l}
  e_1 & e_2 & e_3 & e_4 & e_5 & e_6 & e-7 & e_8 & \\
\begin{block}{[*{8}{r}]@{\quad}l}
  1 & & 1 & & & & & & v_1 \\
-1 & 1 & &1 & & & & & v_2 \\
 & -1 & & & 1 & 1 & & & v_3 \\
 & & & & -1 & -1 & & 1 & v_4 \\
  & & & -1 & & & 1 & -1 & v_5 \\
 & & -1 & & & & -1 & &v_6 \\
\end{block}
\end{blockarray}
\]

\[ A = \begin{array}{r@{\,}*{8}{r}@{\,}l@{}l}
  & e_1 & e_2 & e_3 & e_4 & e_5 & e_6 & e-7 & e_8 & \\
\ldelim[{6}{*} & 1 & & 1 & & & & & & \rdelim]{6}{*} & v_1 \\
& -1 & 1 & &1 & & & & & & v_2 \\
& & -1 & & & 1 & 1 & & & & v_3 \\
& & & & & -1 & -1 & & 1 & & v_4 \\
& & & & -1 & & & 1 & -1 & & v_5 \\
& & & -1 & & & & -1 & & & v_6
\end{array}
\]

\end{document} 

Answer 4

You can use nicematrix and its nice keys like code-for-first-row and code-for-last-col. That way you do not have to type e_1, e_2 etc. nor v_1, v_2 and so on. This also allows you to center the entries of a column or row.

\documentclass{article}
\usepackage{nicematrix}

\begin{document}
\[\pgfmathsetmacro{\myw}{width("$-1$")}
\begin{bNiceArray}{*{8}{R}}[
  first-row,
  last-col,
  code-for-first-row = \makebox[\myw pt][c]{$e_{\arabic{jCol}}$},
  code-for-last-col = v_{\arabic{iRow}}
]
 &  &  &  &  &  &  &  & \\
  1 &     &   1 &     &     &     &     &     &  \\
 -1 &   1 &     &   1 &     &     &     &     &  \\
    &  -1 &     &     &   1 &   1 &     &     &  \\
    &     &     &     &  -1 &  -1 &     &   1 &  \\
    &     &     &  -1 &     &     &   1 &  -1 &  \\
    &     &  -1 &     &     &     &  -1 &     &  \\
\end{bNiceArray}
\]

\end{document}