diagramsxy-pic
I have the following diagram:
\[ \xymatrix @!=1pc {
& Z \ar@{.>}[d]^{\exists!h} \ar@/_1.2pc/[ddl]_{p'} \ar@/^1.2pc/[ddr]^{q'} & \\
& X \times_S Y \ar[dl]_p\ar[dr]^q & \\
X \ar[dr]_f & & Y \ar[dl]^g \\
& S &
} \]
which looks like this:
I want to decrease the spacing between the second and third rows. I know about @R=xpc, but that will decrease the spacing between the first and second rows as well.
If you're using \xymatrix, you can change the row spacing, the column spacing, or both by adding the appropriate command in between the \xymatrix command and the opening brace. The file xyguide.pdf, in section 3.3 (Spacing and Rotation), on page 10, lists the commands as:
@=dimen set spacing @C=dimen set column spacing @R=dimen set row spacing
You use this as in, e.g.,
\begin{equation*}
\xymatrix@C=1em{
{A} \ar[r] \ar[d]
& {B} \ar[d]\\
{C} \ar[r]
& {D}
}
\end{equation*}
You can put the framed y inside a \xybox and then compose it with the ,x,z into the complete object. Together with height adjustment this will look like
\documentclass{standalone}
\usepackage{amsmath,amssymb}
\usepackage[all]{xy}
\begin{document}
\[\xymatrix{
x & *+[Fo]{z} \ar[l]\ar[d] & z\ar[l] & \cdots\ar[l]\\
z & \xybox{(0,0.5)*+[Fo]{y}},x,z \ar[l]\ar[d] & \cdots \ar[l]\\
& *+[Fo]{y} & \cdots\ar[l]
}\]
\end{document}
Although if you would want the circled y aligned with the other circled characters, you should probably ask another question about that. (I don't know right now how to do it.)
Please note that you shouldn't use the minimal class. Better take standalone for MWEs. See for example Why should the minimal class be avoided? and What is the advantage of using minimal over article when creating a standalone graphic?.
Best Answer
You can emulate it by using fake rows: