This is probably best explained with an example. I have the following table, where the "A" cell spans two rows, and the "B" cell spans two columns.
\begin{table}[htdp]
\begin{tabular}{l|r|r}
\multirow{2}{*}{A} & \multicolumn{2}{c}{B} \\
& B1 & B2 \\
a & b1 & b2 \\
a & b1 & b2 \\
\end{tabular}
\end{table}
_ _ _ _ _ _ _ _ _ _ _ _
|A |_ _ _ _B_ _ _ _|
|_ _ _ _|_ _B1_ |_ _B2_ |
|a | b1| b2|
|a | b1| b2|
|a | b1| b2|
|_ _ _ _| _ _ _ |_ _ _ _|
I would like to center the text in the "A" cell, only. I would like to leave the rest of the column left-aligned. Giving:
_ _ _ _ _ _ _ _ _ _ _ _
| A |_ _ _ _B_ _ _ _|
|_ _ _ _|_ _B1_ |_ _B2_ |
|a | b1| b2|
|a | b1| b2|
|a | b1| b2|
|_ _ _ _| _ _ _ |_ _ _ _|
I'm sure this must be simple to do, but I can't seem to put my finger on it.