Question

I have a 3×12 matrix I’d like to input into my LaTeX (with amsmath) document but LaTeX seems to choke when the matrix gets larger than 3×10:

\begin{equation}
\textbf{e} = 
\begin{bmatrix} 
1&1&1&1&0&0&0&0&-1&-1&-1&-1\\
1&-1&0&0&1&1&-1&-1&0&0&1&-1\\
0&0&1&-1&1&-1&1&-1&1&-1&0&0
\end{bmatrix}
\end{equation}

The error: Extra alignment tab has been changed to \cr. tells me that I have more & than the bmatrix environment can handle. Is there a proper way to handle this? It also seems that the alignment for 1’s and the -1’s are different, is that also expected of the bmatrix?

Answer 1

From the amsmath documentation (texdoc amsmath):

The amsmath package provides some
environments for matrices beyond the
basic array environment of LATEX. The
pmatrix, bmatrix, Bmatrix, vmatrix and
Vmatrix have (respectively) ( ), [
], { }, | |, and ∥
∥ delimiters built in. For naming
consistency there is a matrix
environment sans delimiters. This is
not entirely redundant with the array
environment; the matrix environments
all use more economical horizontal
spacing than the rather prodigal
spacing of the array environment.
Also, unlike the array environment,
you don’t have to give column
specifications for any of the matrix
environments; by default you can have
up to 10 centered columns. (If you
need left or right alignment in a
column or other special formats you
must resort to array.)

i.e. bmatrix defaults to a 10 column maximum.

A footnote adds

More precisely: The maximum number of
columns in a matrix is determined by
the counter MaxMatrixCols (normal
value = 10), which you can change if
necessary using LATEX’s \setcounter or
\addtocounter commands.