Matrix within equation

I'd modify the \env@matrix command, on which all the matrix constructions are built; 

\documentclass{article}

\usepackage{amsmath,bm}
\usepackage{setspace}

\usepackage{lipsum} % just for this example

\makeatletter
\def\env@matrix{\hskip -\arraycolsep
  \let\@ifnextchar\new@ifnextchar
  \linespread{1}\selectfont
  \renewcommand{\arraystretch}{1.2}%
  \array{*\c@MaxMatrixCols c}}
\makeatother

\doublespacing

\begin{document}
\lipsum*[2]
\begin{equation}
\mathbf{H} =
 -\bm{\mu} \cdot \mathbf{B} =
 - \gamma B_o \mathbf{S}_z = -\frac{\gamma B_o\hbar}{2}
 \begin{bmatrix} 1&0\\0&-1 \end{bmatrix}.
\end{equation}
\lipsum[3]
\end{document}

Try also without \renewcommand{\arraystretch}{1.2}, that I added in order to space out a bit the rows, which seems better with \doublespacing.

Actually, it's difficult to improve something using \doublespacing, which destroys any attempt at good typography.

enter image description here

In what does this differ from Mico's and Herbert's methods?

Mico's workaround works only within equation. Herbert's instead applies single spacing to all display environments, so also to align, for instance, reducing the line spacing between aligned equations. This might be desirable or not, it depends on you.

Note that {\bf H} should not be used, preferring \mathbf{H}. Also, you'll have noticed that {\bf \mu} doesn't embolden the mu; use \bm{\mu} and load the bm package as in my code.


\documentclass{article}
\usepackage{amsmath}
\usepackage[nodisplayskipstretch]{setspace}
\doublespacing
\everydisplay\expandafter{\the\everydisplay\setstretch{1}}% return to singlespacing

\begin{document}
\begin{equation}
\mathbf{H} = -\mathbf\mu \cdot \mathbf{B} = -\gamma B_o \mathbf{S}_z = -\frac{\gamma B_o\hbar}{2} 
\begin{bmatrix} 1&0\\0&-1 \end{bmatrix}.
\end{equation}

\end{document}

You could use the etoolbox package and use its \AtBeginEnvironment command to reset spacing to \singlespacing at the start of an equation environment.

enter image description here

\documentclass{article}
\usepackage{amsmath}
\usepackage{setspace} % per the OP's information provided in a comment
\doublespacing
\usepackage{etoolbox}
\AtBeginEnvironment{equation}{\singlespacing}
\begin{document}
\begin{equation}
\mathbf{H} = -\boldsymbol{\mu} \cdot \mathbf{B} = - \gamma B_o \mathbf{S}_z = -\frac{\gamma B_o\hbar}{2} 
\begin{bmatrix} 1&0\\0&-1 \end{bmatrix}.
\end{equation}
\end{document}

Remark: This method is quite simple if only the equation environment has to be fixed; it becomes tedious quickly if lots of different display-math environments occur in your document.

Tags:

Equations

Matrices

Math Mode

Setspace

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