Math & Science ⇒ Spacement problem in a column matrix

[Cham]

I have the column-matrix shown below and its last element has a spacement problem : it has a slight horizontal offset, relative to all the other elements in the matrix (see the picture below). Of course, this is because of the size of its "N" index. How can I modify the code below, so the last element is well aligned with all the other elements above it ?

Compilable example :

Code: Select all

\documentclass[12pt]{article}
\usepackage[T1]{fontenc}
\usepackage{lmodern}
\usepackage{amsmath}
\usepackage{tensor}

\begin{document}
	\begin{equation}
		\begin{bmatrix}
			\tensor{\Psi}{_1} \\
			\tensor{\Psi}{_2} \\
			\tensor{\Psi}{_3} \\
			\vdots_{\phantom{3}} \\
			\tensor{\Psi}{_N}
		\end{bmatrix}
	\end{equation}
\end{document}

Here's a preview of the code above :

column.jpg (6.99 KiB) Viewed 2766 times

[Stefan Kottwitz]

Hi Cham,

I wrote earlier in my blog about an extension to the amsmath internal matrix environment, which can be used here. It supports additional positioning options.

If you add to your preamble:

Code: Select all

\makeatletter
\renewcommand*\env@matrix[1][*\c@MaxMatrixCols c]{%
  \hskip -\arraycolsep
  \let\@ifnextchar\new@ifnextchar
  \array{#1}}
\makeatother

then you can write in your code

Code: Select all

\begin{bmatrix}[l]

end there tensors are aligned.

matrix.png (3.4 KiB) Viewed 2760 times

The default centered alignment caused the bad alignment before, since one index was wider.

Stefan

[Cham]

Thanks for the reply.

That solution is working.

However, the vertical dots aren't aligned (centered) with the Psi.

I suspect there's another way. How can I horizonticaly "smash" the "N" index and give to it the same spacing as a "3" ?

[Cham]

O well,

here again, the phantoms are our friends . The code below solves completely my problem :

Code: Select all

\documentclass[12pt]{article}
\usepackage[T1]{fontenc}
\usepackage{lmodern}
\usepackage{amsmath}
\usepackage{tensor}

\begin{document}
        \begin{equation}
                \begin{bmatrix}
                        \phantom{\!{}_1} \tensor{\Psi}{_1} \\
                         \phantom{\!{}_2} \tensor{\Psi}{_2} \\
                         \phantom{\!{}_3} \tensor{\Psi}{_3} \\
                         \phantom{\!{}_3} \vdots_{\phantom{3}} \\
                         \phantom{\!{}_N} \tensor{\Psi}{_N}
                \end{bmatrix}
        \end{equation}
\end{document}