[Tex/LaTex] Expression under summation on multiple lines

math-modemath-operators

Possible Duplicate:
Separate long math text under sum symbol into different lines?

I want to write expression \sum_{i=0}^n i with i\neq 4 under the
summation symbol. How can I write this?

Best Answer

You can use \substack:

If this is desired in inline math you can use \limits to obtain the limits underneath the summation symbol:

However this is not recommended as it may not look good depending on how much adjacent text there is as it will affect interline spacing.

Code:

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\[
  \sum_{\substack{i=0 \\ i\neq 4}}^n i
\]

In inline math: $\sum_{\substack{i=0 \\ i\neq 4}}^n i$, or
$\sum\limits_{\substack{i=0 \\ i\neq 4}}^n i$
\end{document}

Related Solutions

[Tex/LaTex] Separate long math text under sum symbol into different lines

You can use the \substack command from the amsmath package, like this:

\begin{equation}
  d(\vec{x},\vec{y}) =
  \sum_{\substack{Z_{xy}\in\vec{Z}_{xy}\\
                  \forall x\in\vec{x}\\
                  \forall y\in\vec{y}}}
        f(Z_{xy}) 
\end{equation}

However, the result still doesn’t look good, because of the extra spacing around the sum symbol:

$Image showing the result of the ‘\substack’ command$

To fix this, you can use the \mathclap command from the mathtools package, like this:

\begin{equation}
 d(\vec{x},\vec{y}) =
    \sum_{\mathclap{\substack{Z_{xy}\in\vec{Z}_{xy}\\
                              \forall x\in\vec{x}\\
                               \forall y\in\vec{y}}}}
          f(Z_{xy}) 
\end{equation}

$Image showing the result of the ‘\mathclap’ and ‘\substack’ commands$

But perhaps you might be happy using only \mathclap, and not \substack. The result looks good as long as the subscript is not too wide.

\begin{equation}
  d(\vec{x},\vec{y}) =
    \sum_{\mathclap{{Z_{xy}\in\vec{Z}_{xy},
          \forall x\in\vec{x},
          \forall y\in\vec{y}}}} f(Z_{xy})
\end{equation}

$Image showing the result of the ‘\mathclap’ command$

The mathtools package also have several other useful commands for typesetting mathematics, including more commands for improving the display of subscripts and superscripts. I very much recommend taking a look at its documentation.

[Tex/LaTex] XOR and II (concatenation) summation symbols

You want to use \bigoplus instead of \oplus.

I've never seen concatenation done that way. Addition and XOR are commutative operations so it makes sense to sum over a set (or take the exclusive OR of a set). Concatenation is not like that. I think I would explicitly write out the concatenation. That said, you can use \bigparallel from the stmaryrd package.

\documentclass{article}
\usepackage{amsmath}
\usepackage{stmaryrd}
\newcommand*\concat{\mathbin{\|}}
\begin{document}
\[x_1\concat x_2\concat\dotsb\concat x_n\]
\[\bigparallel_{i=1}^n x_i\]
\end{document}

enter image description here