Xy-pic User's Guide
*object form described above can be used to space
individual objects differently, however, it is also possible to
change the overall spacing of a matrix by inserting the
following codes between \xymatrix and the following {: @=dimen | set spacing |
@R=dimen | set row spacing |
@C=dimen | set column spacing |
@M=dimen | set entry default margin |
@W=dimen | set entry default width |
@H=dimen | set entry default height |
@L=dimen | set label margin |
= can be replaced by any of +, +=, -,
and -= of section 2.2 with the same meaning,
i.e., replace "set" with "increase," "increase to at most,"
"decrease," and "decrease to at least," respectively. For example,
$\xymatrix@1@=0pt@M=0pt{A&B\\C&D}$ in the text typesets 
.
In case uniform spacing is desired, several alternative forms exist.
@! | force all spaces equal |
@!0 | -- and ignore entry sizes |
@!R | force equal row spacing |
@!C | force equal column spacing |
Finally a special notation allows rotation of an entire matrix:
@d | rotate towards d |
Only the matrix grid will rotate, however, not the actual contents.
Xy-pic User's Guide