# Commutative Diagrams

Can anyone help me in giving commands for commutative diagrams in LaTeX ? It doesn't seem to appear properly in the LaTeX guides that I have. A command for a simple triangular diagram with arrows associated to maps would be good enough, or maybe some appropriate reference.

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sure, how about a quick google –  cmhughes May 23 '13 at 15:28
Take a look at jmilne.org/not/CDGuide.html –  Papiro May 23 '13 at 15:29
One single authentic source on xy-pic is at TUG and its userguide and crisp Introduction ppt. More in depth reference guide –  texenthusiast May 23 '13 at 15:34
The most modern package is tikz-cd. The documentation includes numerous examples. –  Gonzalo Medina May 23 '13 at 15:38

For simple and complex diagrams, I'd recommend tikz-cd. Let's see an easy triangular diagram.

\documentclass{article}
\usepackage{tikz-cd}
\begin{document}
$\begin{tikzcd} A \arrow{r}{f} \arrow[swap]{dr}{g\circ f} & B \arrow{d}{g} \\ & C \end{tikzcd}$
\end{document}


An arrow takes as argument the "steps" where it has to go: r stands for "right", d stands for "down"; also u stands for "up" and l for "left".

A similar syntax is available with Xy-pic.

\documentclass{article}
\usepackage[all,cmtip]{xy}
\begin{document}
$\xymatrix{ A \ar[r]^{f} \ar[dr]_{g\circ f} & B \ar[d]^{g} \\ & C }$
\end{document}


Note how the labels are positioned: ^ means above the arrow, _ means below; above and below are with respect to the direction of the arrow: rotate it counterclockwise until it points from left to right.

As you see, the results are pretty much alike. While I used to use Xy-pic, I'm now more convinced that tikz-cd can be better, as it relies on the powerful TikZ/PGF library.

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Thanks, that's very helpful :) –  smiley06 May 25 '13 at 8:30