[Tex/LaTex] Bad math environment delimiter when using \begin{equation} and \end{equation}

equationsmatrices

I wrote a matrix equation

\[
  \left[ \begin{array}{c}
    v^{0}_{n} \\
    v^{K-1}_{n}
  \end{array} \right] = 
    -\frac{1}{C_{ref}} 
      \left[ \begin{array}{ccc} V^{0}_{0,n} & \cdots & V^{0}_{M-1,m} \\
        \vdots & \ddots & \vdots \\
        V^{K-1}_{0,n} & \cdots &  V^{K-1}_{M-1,n}
      \end{array}  \right]
      \left[ \begin{array}{c}
        C_{0,n} \\
        C_{M-1,n}
      \end{array}
  \right]
\]

I want to put an equation number at the end of this equation. But only way I know how to do that is to put this whole equation in \begin{equation} and \end{equation} which gives an error. The error is

Bad math environment delimiter

When I delete \[ and \] from the start and end of my equation, I no longer get an error. My question is that why am I getting this error just by moving an equation in \begin and \end.

Best Answer

The LaTeX macros \begin{equation} and \[ both initiate a display-math group, and the macros \end{equation} and \] both terminate a display-math group. (In addition, the equation environment provides a method for numbering the equations, whereas \[ ... \] does not.) The LaTeX macros \begin{equation} and \[ are designed purposefully so as not to let users open a display-math group twice; this is why you're getting the error message "Bad math environment delimiter" when LaTeX encounters \[ after having processed \begin{equation}.

The upshot: Use one or the other method for setting up a display-math group, but don't use both simultaneously.

For a more-detailed discussion of how various LaTeX displaymath environments are set up, see this answer to the question "What are the differences between $$, \[, align, equation and displaymath?" Shameless self-citation alert!

Related Solutions

[Tex/LaTex] List of equations, including equation contents and caption

Since you want a cheat sheet, I'd recommend the extract package. With a slightly different MWE:

\documentclass{article}
\usepackage[
  active,
  header=false,
  copydocumentclass=true,
  generate=\jobname-Cheatsheet,
  extract-env={equation},
  extract-cmdline={synopsis},
  ]{extract} % http://ctan.org/pkg/extract
\begin{extract*}
% Items executed in both the main and extracted document
% (extract manual, section 5.1)
\usepackage{amsmath}
\end{extract*}
\begin{extract}
% Items executed only in extracted document
\def\synopsis#1{#1}
\end{extract}
\def\synopsis#1{}
\begin{document}
First Euler observed that
\synopsis{Euler's equation tying together the five fundamental constants of mathematics}%
\begin{equation}
1 + e^{i \Pi} = 0.
\end{equation}

Then, Gauss discovered the normal distribution:
\synopsis{Normal distribution}%
\begin{equation}
P(x) = \frac{1}{{\sigma \sqrt {2\pi } }}e^{{{ - \left( {x - \mu } \right)^2 } \mathord{\left/ {\vphantom {{ - \left( {x - \mu } \right)^2 } {2\sigma ^2 }}} \right. \kern-\nulldelimiterspace} {2\sigma ^2 }}}
\end{equation}

Finally, Einstein proclaimed: 
\synopsis{Equivalence of mass and energy}%
\begin{equation}
E = m C^2
\end{equation}
\end{document}

you get an original document of:

enter image description here

and an extracted document of:

\documentclass{article}
% Items executed in both the main and extracted document
% (extract manual, section 5.1)
\usepackage{amsmath}
% Items executed only in extracted document
\def\synopsis#1{#1}

\begin{document}

\synopsis{Euler's equation tying together the five fundamental constants of mathematics}%

\begin{equation}
1 + e^{i \Pi} = 0.
\end{equation}

\synopsis{Normal distribution}%

\begin{equation}
P(x) = \frac{1}{{\sigma \sqrt {2\pi } }}e^{{{ - \left( {x - \mu } \right)^2 } \mathord{\left/ {\vphantom {{ - \left( {x - \mu } \right)^2 } {2\sigma ^2 }}} \right. \kern-\nulldelimiterspace} {2\sigma ^2 }}}
\end{equation}

\synopsis{Equivalence of mass and energy}%

\begin{equation}
E = m C^2
\end{equation}

\end{document}

and:

enter image description here

This also works with your original \caption command.

[Tex/LaTex] Bad math environment delimiter. \end{equation}

I think the following may be what you're looking to write. Observe the use of \text in the numerator and denominator of the first equation. I encased the term X in the first numerator in $ symbols to inform LaTeX that it (the X) should be processed in math mode.

Observe also that there must be no blank lines in a display-math environment (such as equation).

\documentclass{article}

\usepackage{amsmath} % for "\text" and "\DeclareMathOperator" macros
\DeclareMathOperator{\Support}{Support}
\DeclareMathOperator{\Confidence}{Confidence}

\begin{document}

\begin{equation}
\Support(X) = \frac{\text{No of transactions that contain $X$}}%
                   {\text{No of transactions in the database}}
\end{equation}

\begin{equation}
\Confidence(X \longrightarrow Y) = \frac{\Support(X\cup Y)}{\Support(X)}
\end{equation}

\end{document}

Best Answer

Related Solutions

[Tex/LaTex] List of equations, including equation contents and caption

[Tex/LaTex] Bad math environment delimiter. \end{equation}

Related Question