When studying systems of linear equations, it's nice to remind people that the last column of the coefficient matrix holds the constants. This is often done in books by putting a vertical line between the last column and the next to last column. What is a good way to do this in LaTex?
One way to do this is implemented in the (free, in both senses!) online linear algebra textbook Linear Algebra by Jim Hefferon. It's written in LaTeX and is open-source so one can download the book and its attendant style files. One of them, called
and is used as:
(note that the argument is one less than the total number of columns). I guess that the
That style file has several other useful linear algebra macros that may be useful.
If you build your own environment using array, you're on the safe side. I would extend an internal macro of amsmath using an optional argument.
Here's the redefinition, just put it in your preamble after loading amsmath:
I had to use
So, there's not much that's been changed.
Simple augmented matrix:
More complex use, with different alignment, spacing and color:
Just remove the optional argument in brackets and you will get the standard pmatrix or bmatrix.
I've used this code and examples in a blog post in 2008: An extension to amsmath matrix environments.
If you don't wish to redefine that internal macro, you could give it a different name and build your amatrix environment on it exactly the same way that amsmath does with pmatrix.
If you are using an array to input the matrix, you just have to specify something like
Edit: Here's an example. I'm actually not thrilled about the spacing.