Math & Science ⇒ Line around the diagonal of a matrix

[kapowza]

I have a matrix

Code: Select all

$\begin{pmatrix}
a & b & c \\
d & e & f \\
g & h & i
\end{pmatrix}$

and I'd like to be able to draw a loop around the diagonal a-e-i. I know that I've seen something similar using tikz matrix in the past, but I can't figure it out now. Any ideas? Also, what if I wanted to draw a basic line through the diagonal instead of around it?

[localghost]

[…] I know that I've seen something similar using tikz matrix in the past, but I can't figure it out now. Any ideas? Also, what if I wanted to draw a basic line through the diagonal instead of around it?

If so, take a look at the pgf/tikZ manual or at some examples [1]. Otherwise the »Math mode« document may help.

[1] TikZ examples feature: Matrices


Best regards
Thorsten¹

[kapowza]

If anyone's having the same issue that I was, I found a partial solution on page 109 of the "Math mode" document using the cline command - it shows how to make a box around a row or column. I'm still unsure how to get a box around the diagonal of a matrix, but if I make any progress, I'll post here.