Error "Missing $ inserted. \end{align*}" on the tabular environment

Question

Hey guys i'm getting this error in my tabular environment, is there something about the tabular environment that I'm missing, it's not a math mode, so I embbed it in an align*, or gather* but it doesn't compile well.

    \documentclass[12pt, letterpaper, oneside]{article}
    \usepackage{amsmath}
    \usepackage{amsthm}
    \usepackage{mathtools}
    \usepackage{tabularx}

    \begin{document}
        If not compiling, hit ctrl+z on the whole align* environment, leave this sentence, and compile the thing again, and then paste the code and compile it once more.
    \begin{align*}
        \begin{tabular}{c|cccccc}
            & -2 & -1 & 0 & 1 & 2 & 3\\ 
            \hline
            q_i & & & 1 & 1 & 3 & 5\\
            r_i & 703 & 399 & 304 & 95 & 19 & 0\\
            u_i & 1 & 0 & 1 & -1 & 4 & -21\\
            v_i & 0 & 1 & -1 & 2 & -7 & 37
        \end{tabular}
    \end{align*}
\end{document}

Any help will be appreciated :)

Answer 1

You should make two separate changes.

• The contents of the table -- not only the left-hand header column, but the 6 data columns as well -- need to be typeset in math mode rather than in text mode. I therefore suggest you switch from a tabular to an array environment.

• You're abusing and misusing the align* environment. Please use \[ and \] instead of \begin{align*} and `\end{align*}.

Optionally, change the column type of the 6 data columns from c to r.

\documentclass[12pt, letterpaper]{article}
\usepackage{array}
\begin{document}
\[
\begin{array}{c|rrrrrr}
    &  -2 &  -1 &   0 &  1 &  2 &   3 \\ 
\hline
q_i &     &     &   1 &  1 &  3 &   5 \\
r_i & 703 & 399 & 304 & 95 & 19 &   0 \\
u_i &   1 &   0 &   1 & -1 &  4 & -21 \\
v_i &   0 &   1 &  -1 &  2 & -7 &  37
\end{array}
\]
\end{document}