LaTeX How do you make a circled number using LaTeX

[bwpbruce]

There's a tutorial posted on how to make a circled number in LaTeX:
tikz pgf - Good way to make \textcircled numbers? - TeX - LaTeX Stack Exchange

however, it doesn't seem to work here. Why not?

 

[MarkFL]

There may be other ways, but one way to enclose something in a circle is to use:

\enclose[mathcolor="color"]{circle}{expression}

The color is optional...if omitted, the circle will be black.

For example, the following code:

$$\enclose{circle}[mathcolor="red"]{\frac{x}{y}}$$

produces:

$$\enclose{circle}[mathcolor="red"]{\frac{x}{y}}$$

 

[bwpbruce]

Thank you. All I wanted to be able to do is this:

\begin{bmatrix} \enclose{circle}1 & 0 & 0 \\ 0 & 1 & 0 \\ 0 & 0 & 1 \end{bmatrix}