# isomorphism in xymatrix

Consider the tex:

\xymatrix{
M \ar[r]^{f}\ar[d]_{h} & N \ar@{-->}[dl]^{g} \\
P}


If f is isomorphism, not identity. How to change the tex? If I replace \ar[r]^{f} by \ar@{\cong }[r]^{f}, this can't work. How to get isomorphism?

• (1) welcome, (2) as always on this site you are much much more likely to get help if you provide a full minimal example others can copy and test as is. – daleif Jan 31 at 14:06

The usual way would be to add \cong under the arrow:

\documentclass{article}

\usepackage[all]{xy}

\begin{document}

\xymatrix{
M \ar[r]^{f}_{\cong} \ar[d]_{h} & N \ar@{-->}[dl]^{g} \\
P}

\end{document}


The \ar@... syntax tries to change the arrow type, but there is not really a standard arrow symbol for isomorphism.