Latex: Determinant

Lucimeire83 · #1 $Old$ November 24th, 2008, 05:47 AM

Hi

I'm trying to add some braces above/below and left/right of a Determinant to describe how many Columns and Rows certain ranges of the matrix has.
For example I have a 2 by 2 Block-matrix. I want a brace over the first and the one over the second column telling me how large each blockdeterminant is.

I hope someone knows a solution to this problem.

Opalg · #2 $Old$ November 24th, 2008, 06:42 AM

Plain TeX has a macro called \bordermatrix that lets you put labels above the columns and to the left of the rows. It can give you things like this:

$M = \bordermatrix{&\overbrace{}^{\textstyle m}&\overbrace{}^{\textstyle n}\cr p\{&A&B\cr q\{&C&D\cr}$

Code:

 M = \bordermatrix{&\overbrace{}^{\textstyle m}
 &\overbrace{}^{\textstyle n}\cr 
 p\{ &A&B\cr q\{ &C&D\cr}

As far as I know, there is no LaTeX version of this, so you have to use the plain TeX syntax, with for example \cr instead of \\ for the carriage returns.

Lucimeire83 · #3 $Old$ November 24th, 2008, 07:28 AM

OPALG, Thank you for your help, but I think that \bracematrix use just for matrix and I want to use for a determinant.

Opalg · #4 $Old$ November 24th, 2008, 01:58 PM

Ahem, yes. You'd think I might have noticed that very conspicuous bolded word Determinant

So, the best I can do is a really ugly kludge that produces $\begin{array} {r|@{\hspace{9pt}}c@{\hspace{12pt}}c@{\hspace{9pt}}|} \multicolumn{3}{r@{\hspace{1pt}}}{\overbrace{}^{\textstyle m} \overbrace{}^{\textstyle n}} \\ p\,\{&A&B\\ q\,\{&C&D \end{array}$ .

Code:

\begin{array}
{r|@{\hspace{9pt}}c@{\hspace{12pt}}c@{\hspace{9pt}}|}
\multicolumn{3}{r@{\hspace{1pt}}}{\overbrace{}^{\textstyle m}
\overbrace{}^{\textstyle n}} \\  p\,\{&A&B\\ q\,\{&C&D \end{array}

This has the drawback that it isn't well aligned vertically. If you want to put it in a formula like $M = \begin{array} {r|@{\hspace{9pt}}c@{\hspace{12pt}}c@{\hspace{9pt}}|} \multicolumn{3}{r@{\hspace{1pt}}}{\overbrace{}^{\textstyle m} \overbrace{}^{\textstyle n}} \\ p\,\{&A&B\\ q\,\{&C&D \end{array}$ then you'll want to raise it by putting it into an \hbox along with a \raise command, as in
$M = \raise2ex\hbox{$\begin{array}{r|@{\hspace{9pt}}c@{\hspace{12pt}}c@{\hspace{9pt}}|}\multicolumn{3}{r@{\hspace{1pt}}}{\overbrace{}^{\textstyle m} \overbrace{}^{\textstyle n}} \\ p\,\{&A&B\\ q\,\{&C&D \end{array}$}$ .