Possible Duplicate:
How to draw a commutative diagram?
Today i wanted to include a drawing of a commutative diagram in my answer on math.stackexchange.com - but did not find any way of doing that.
Isn't there yet such a thing to render $$\xymatrix{\ar @{} [dr] |{\#} P \ar[r]^f \ar[d]_\pi & P \ar[d]^\pi \\ M \ar[r]_{\bar f} & M }$$ or is it that i used the wrong syntax. If it is not included i would make this a feature request.
xy
and similar packages aren't implemented in MathJaX, yet. See here for the list of available commands and see also this discussion on meta.MO. $\endgroup$