I need to use the xy
maths package (because I need to make it into a PNG file for Wordpress and mathurl.com accepts the xy
template) to make a commutative diagram in which there are diagonal 4 shorter arrows inside the diagram, directed inward. The best I can do is
\usepackage[all]{xy}
\xymatrix{Y' \ar[r]^{g'}
\ar[d]_{f'} & X' \ar[d]^{f} \\
Y \ar[r]_{g} & X
\\
%
\ar@{=>}"1,2"*++++\frm{};"2,1"*++\frm{}}
So I can only get one arrow, which needs to be higher up to the right.
{}
above the text field (or hitting Ctrl + K). – Torbjørn T. Mar 31 '12 at 13:58\xymatrix{Y' \ar[r]^{g'} \ar[d]_{f'} & X' \ar[d]^{f} \Y \ar[r]_{g} & X \\ar@{=>}"1,2"*++\frm{};"2,1"*++\frm{} \ar@{=>}"1,1"*++\frm{};"2,2"*++\frm{}}
– Gonzalo Medina Mar 31 '12 at 14:49