====== matrix data ======
\begin{eqnarray*}
A = 
\begin{bmatrix}
2 & 6 & 3 \\
4 & 1 & 5 \\
\end{bmatrix}
\end{eqnarray*}

<code>
A <- c(2, 4, 6, 1, 3, 5)
A
dim(A) <- c(2, 3)
A
class(A)
</code>

<code>
A <- c(2, 4, 6, 1, 3, 5)
A
AbyCol <- matrix(nrow=2, ncol=3, A)
AbyCol
AbyRow <- matrix(nrow=2, ncol=3, A, byrow=T)
AbyRow
</code>

<code>
A <- c(2, 4, 6, 1, 3, 5)
A
AbyCol <- matrix(nrow=2, ncol=3, A)
AbyCol
AbyRow <- matrix(nrow=2, ncol=3, A, byrow=T)
AbyRow
</code>