How can i write my own math operator with limits? I want it to look like:
\sum\limits_{e=1}^{m}
but with a capital A (if possible bigger than the normal text) instead of the sum.
Thanks for the help!
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5 Answers
We can scale the symbol to the height plus depth of the summation and then vertically center it with respect to the formula axis.
\documentclass{article}
\usepackage{amsmath}
\usepackage{graphicx}
\makeatletter
\DeclareRobustCommand\bigop[1]{%
\mathop{\vphantom{\sum}\mathpalette\bigop@{#1}}\slimits@
}
\newcommand{\bigop@}[2]{%
\vcenter{%
\sbox\z@{$#1\sum$}%
\hbox{\resizebox{\ifx#1\displaystyle.9\fi\dimexpr\ht\z@+\dp\z@}{!}{$\m@th#2$}}%
}%
}
\makeatother
\newcommand{\bigstar}{\DOTSB\bigop{\star}}
\newcommand{\bigA}{\DOTSB\bigop{\mathrm{A}}}
\begin{document}
\[
\sum_{i=1}^n\bigA_{i=1}^n x_i\dots\bigstar_{i=1}^n x_i
\qquad
\textstyle
\sum\bigA\bigstar_{i=1}^n x_i
\qquad
\scriptstyle
\sum\bigA\bigstar_{i=1}^n x_i
\qquad
\scriptscriptstyle
\sum\bigA\bigstar_{i=1}^n x_i
\]
\end{document}
A simpler but not not scalable version (it won't work in
\newcommand{\opA}{\mathop{\vphantom{\sum}\mathchoice
{\vcenter{\hbox{\huge A}}}
{\vcenter{\hbox{\Large A}}}{\mathrm{A}}{\mathrm{A}}}\displaylimits}
In this way the "A" will be as large as the \sum symbol.
An enhanced version, where one can specify a correction factor for the big symbol in display style, as different symbols seem to require different factors.
\documentclass{article}
\usepackage{amsmath}
\usepackage{graphicx}
\makeatletter
\DeclareRobustCommand\bigop[2][1]{%
\mathop{\vphantom{\sum}\mathpalette\bigop@{{#1}{#2}}}\slimits@
}
\newcommand{\bigop@}[2]{\bigop@@#1#2}
\newcommand{\bigop@@}[3]{%
\vcenter{%
\sbox\z@{$#1\sum$}%
\hbox{\resizebox{\ifx#1\displaystyle#2\fi\dimexpr\ht\z@+\dp\z@}{!}{$\m@th#3$}}%
}%
}
\makeatother
\newcommand{\bigstar}{\DOTSB\bigop{\star}}
\newcommand{\bigA}{\DOTSB\bigop[0.92]{\mathrm{A}}}
\newcommand{\bigDelta}{\DOTSB\bigop[1.05]{\Delta}}
\begin{document}
\[
\sum_{i=1}^n\bigA_{i=1}^n\bigDelta_{i=1}^n x_i\dots\bigstar_{i=1}^n x_i
\]
\begin{center}
$\textstyle
\sum \bigA \bigstar \bigDelta_{i=1}^n x_i
\qquad
\scriptstyle
\sum \bigA \bigstar \bigDelta_{i=1}^n x_i
\qquad
\scriptscriptstyle
\sum \bigA \bigstar \bigDelta_{i=1}^n x_i
$
\end{center}
\end{document}
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I'd like to do the same but using
\star. What are the 4 sizes used in the choice? I'd like to use\LARGE\star. Is there different sizes for display or inline math?– SigurMay 11, 2015 at 13:48 -
@Sigur I added the code for the big star; I used just 90 percent of the size of a summation symbol, because the star has large overshoot.– egregMay 11, 2015 at 15:21
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thanks so much. Amazing and beautiful. Since I like to use
\textstylesize in displayed mode (the\sumin displaystyle is too big in my opinion) should I use\vphantom{\textstyle\sum}?– SigurMay 11, 2015 at 15:32 -
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sorry. Use it where? In the text body? If I well understood, you made a box with the same height as the one produced by
\sum. But every time I use\sumin display mode I use\textstyleand\limitso make the summation smaller. I'd like to define the star symbol in such a way that I don't need to use\textstyleinside display mode. Simply\[ \bigstar_{i=1}^n\]with the same size as\[ \textstyle \bigstar\limits_{i=1}^n\].– SigurMay 11, 2015 at 15:43
Use the \DeclareMathOperator* command provided by the amsmath package. Example:
\documentclass{article}
\usepackage{amsmath}
\DeclareMathOperator*{\Aop}{A}
\begin{document}
\[ \Aop^a_b \]
\end{document}
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4Where is the difference between
\DeclareMathOperator*and\DeclareMathOperator? Jan 9, 2016 at 21:53 -
11@moose
\DeclareMathOperator*will use limits so subscript/superscript will go directly below and above the symbol, while\DeclareMathOperatorwill not use limits and so subscript/superscript will go below right and above right.– BakuriuJan 30, 2016 at 9:25
\documentclass{article}
\usepackage{amsmath}
\def\Aop{\operatornamewithlimits{%
\mathchoice{\vcenter{\hbox{\huge A}}}
{\vcenter{\hbox{\Large A}}}
{\mathrm{A}}
{\mathrm{A}}}}
\begin{document}
\[ \Aop^a_b \sum_a^b \]
$ \Aop^a_b \sum_a^b $
\end{document}
Use \mathop to turn A into a "math operator", and then use \limits to do sum-style limits:
$$\mathop{A}\limits_{e=1}^{m}$$
Do you really want A, or do you want \bigwedge?
answered Jul 18, 2011 at 19:25
egreg's answer is fine but works poorly for existing mathematical symbols. I recommend the following:
\newcommand{\operator}[1]{\mathop{\vphantom{\sum}\mathchoice
{\vcenter{\hbox{\huge $#1$}}}
{\vcenter{\hbox{\Large $#1$}}}{#1}{#1}}\displaylimits}
To define an operator 'A', you can now type
\newcommand{\opA}{\operator{\mathrm{A}}}
But you can also define an operator Theta:
\newcommand{\opTheta}{\operator{\Theta}}
Just remember that in the argument you pass to \operator, you are in math mode.
