我想表達所有離散狀態的總和以及所有連續狀態的積分。通常，此標誌是$\sum$疊加在 上的$\int$。有沒有指令可以製作這個符號？如果不是的話，能否通過和與積分符號以某種方式組合起來？
答案1
這是Unicode字元庫 > 符號庫 > 符號 > 積分求和 (U+2A0B)(⨋)。它可與STIX 字體。 （目前 Beta 測試中支援 LaTeX。）相關命令是\sumint。
答案2
您可以建立符號：
\documentclass{article}
\usepackage{amsmath}
\usepackage{graphicx}
\DeclareMathOperator*{\SumInt}{%
\mathchoice%
{\ooalign{$\displaystyle\sum$\cr\hidewidth$\displaystyle\int$\hidewidth\cr}}
{\ooalign{\raisebox{.14\height}{\scalebox{.7}{$\textstyle\sum$}}\cr\hidewidth$\textstyle\int$\hidewidth\cr}}
{\ooalign{\raisebox{.2\height}{\scalebox{.6}{$\scriptstyle\sum$}}\cr$\scriptstyle\int$\cr}}
{\ooalign{\raisebox{.2\height}{\scalebox{.6}{$\scriptstyle\sum$}}\cr$\scriptstyle\int$\cr}}
}
\begin{document}
$\SumInt_{\SumInt} \displaystyle\SumInt$
\end{document}
該MnSymbol軟體包提供\sumint（使用它一些符號會改變）：
\documentclass{article}
\usepackage{MnSymbol}
\begin{document}
$\sumint_{\sumint} \displaystyle\sumint$
\end{document}
答案3
其他選項是mathtools包：
\documentclass{article}
\usepackage{mathtools}
\begin{document}
$\int\mathllap{\sum}$
$\mathclap{\displaystyle\int}\mathclap{\textstyle\sum}$
$F(y)=\mathclap{\displaystyle\int}\mathclap{\textstyle\sum}\;\;\; f(y)\,\mathrm dy$
\end{document}
由於 tohecz 註釋指出的符號周圍的間距問題，此 tex 檔案中有更多有用的範例。大字元中的第一個範例獲得與使用完全相同的輸出\ooalign{$\textstyle\sum$\cr\hidewidth$\displaystyle\int$\hidewidth\cr}
\documentclass[10]{article}
\usepackage{mathtools}
\usepackage{xcolor}
% Reference shadow equation without \int
\newcommand{\refereq}{
\textcolor{cyan}{
$F(y)= \sum f(y)\,\mathrm dy$
}\par\vspace{-1.41\baselineskip}\par}
\begin{document}
\bigskip
Test inside formula \emph{vs}
normal position of $\scriptstyle\sum$
(cyan shadow without
$\scriptstyle\int$):
\bigskip
{\Huge \refereq
$F(y)=
\mathrlap{\displaystyle\int}
\mathrlap{\textstyle\sum}
\phantom{\mathrlap{\displaystyle\int}
\textstyle\sum}
f(y)\,\mathrm dy$}
\bigskip
Note that different symbol combinations
with {\tt mathtools} have different
spacing effects: \\
\bigskip
\begin{tabular}{l|l|ll}
& Symbol & Size & Alignment \\
1 & $\sum$ x
& \textbackslash{textstyle}
& normal \\
& $\displaystyle\sum$ x
& \textbackslash{display}
& normal\\
2 & $\int$ x
& \textbackslash{textstyle}
& normal \\
& $\displaystyle\int$ x
& \textbackslash{display}
& normal\\
3 & $\int\mathllap{\sum}$ x
& \textbackslash{textstyle}
& \textbackslash{}math{\bf l}lap
\{$\scriptstyle\sum$\} \\
4 & $\displaystyle\int\mathllap{\sum}$ x
& \textbackslash{displaystyle}
& \textbackslash{}math{\bf l}lap
\{$\scriptstyle\sum$\} \\
5 & ${\displaystyle\int}
\mathllap{\sum}$ x
& mixed
& \textbackslash{}math{\bf l}lap
\{$\scriptstyle\sum$\} \\
6 & $\mathclap{\displaystyle\int}\mathclap{\textstyle\sum}$ x
& mixed
& \textbackslash{}math{\bf c}lap (both) \\
7 & $\mathrlap{\displaystyle\int}\textstyle\sum$ x
& mixed
& \textbackslash{}math{\bf r}lap\{$\int$\}\\
8 & $\mathrlap{\displaystyle\int}\mathrlap{\textstyle\sum} $ x
& mixed
& \textbackslash{}math{\bf r}lap (both) \\
9 & $\mathllap{\displaystyle\int}\mathllap{\textstyle\sum}$ x
& mixed
& \textbackslash{}math{\bf l}lap (both) \\
\end{tabular}
\bigskip
Comments:
Note that there are little differences
inside the combined symbol. With respect
(8) in (5) and (9) and even in (6) the
$\int$ is lightly displaced to the
rigth, but in (7) is left displaced.
\bigskip
\refereq
$F(y)=
{\displaystyle\int}\mathllap
{\textstyle\sum}
f(y)\,\mathrm dy$
(5) f is spaced from
$\scriptstyle\int$ but is too
near to $\scriptstyle\sum$
\refereq
$F(y)=
\hspace{.5em}\mathclap{\displaystyle
\int}\mathclap{\textstyle\sum}
\hspace{.5em}
f(y)\,\mathrm dy$
(6) Need extra .5em in both sides
to look as (5).
\refereq
$F(y)=
\mathrlap{\displaystyle\int}
\textstyle\sum
f(y)\,\mathrm dy$
(7) f well spaced from
$\scriptstyle\sum$ (but
$\scriptstyle\int$ is too left?)
\refereq
$F(y)=
\mathrlap{\displaystyle\int}
\mathrlap{\textstyle\sum}
\phantom{\mathrlap{\displaystyle
\int}\textstyle\sum}
f(y)\,\mathrm dy$
(8) Need recover right space
but then fit perfectly.
\refereq
$F(y)=
\phantom{\textstyle\sum}
\mathllap{\displaystyle\int}
\mathllap{\textstyle\sum}
\phantom{\mathrlap{
\displaystyle\int}}
f(y)\,\mathrm dy$
(9) Need recover left space
to see just as (5).
So, better approach (with
{\tt mathtools}, of course),
seem to be (8)
\end{document}
