How to write an arbitrary Math symbol larger like summation?

Question

I want to write something like this

I have tried something like (requires relsize package for using \larger[]{})

$$\mathop{\mathop{\text{\larger[5] C}}_{i=1}^{i=N-1}}_{j=i+1}^{j=N} t_i t_j$$

But, the problem is, symbols don't get aligned correctly (centered on the letter) like in the usual Sum expression, as you can see below -

Can anything be done here?

Look up \DeclareMathOperator* in the amsmath user guide. — barbara beeton, Jul 25 '23 at 02:02
I can see this makes it possible to have our own mathematical operator, and the function with '*' at the end helps to have superscript and subscript under and above the particular math operator. But, as I try to make the text 'C' bigger using \text{\larger[5] C}, this creates the same output. The centering doesn't work in text mode, maybe? The \mathlarger{} doesn't take any font size type parameter like \larger[]{} do, and it doesn't increase the font that much! — akopty, Jul 25 '23 at 02:35
Don't use $$ in LaTeX for displayed maths, instead use \[ and \] or the equation environment. $$ isn't really supported by LaTeX and can lead to improper spacing. — Skillmon, Jul 25 '23 at 03:59

score 4 · Accepted Answer · edited Jul 25 '23 at 03:59

4

Use

$$\mathop{\mathop{\vcenter{\larger[5]\hbox{C}}}_{i=1}^{i=N-1}}_{j=i+1}^{j=N} t_i t_j$$

Explanation: The \vcenter primitive centers its material vertically to math axis and the \hbox protect opening paragraph mode, i.e. the \parindent space before the big C.

edited Jul 25 '23 at 03:59

Skillmon

60,462

answered Jul 25 '23 at 03:41

wipet

74,238

score 4 · Answer 2 · answered Jul 25 '23 at 09:06

You can combine https://tex.stackexchange.com/a/23436/4427 and https://tex.stackexchange.com/a/205520/4427

You need to judge by eye the correction factor 0.92, because different characters tend to have different behaviors.

\documentclass{article}
\usepackage{amsmath,graphicx}
\makeatletter
% https://tex.stackexchange.com/a/23436/4427
\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@}{!}{$\m@th#3$}}%
  }%
}
% https://tex.stackexchange.com/a/205520/4427
\newcommand{\subalign}[2][c]{%
  \if#1c\vcenter\else\vtop\fi{%
    \Let@ \restore@math@cr \default@tag
    \baselineskip\fontdimen10 \scriptfont\tw@
    \advance\baselineskip\fontdimen12 \scriptfont\tw@
    \lineskip\thr@@\fontdimen8 \scriptfont\thr@@
    \lineskiplimit\lineskip
    \ialign{\hfil$\m@th\scriptstyle##$&$\m@th\scriptstyle{}##$\hfil\crcr
      #2\crcr
    }%
  }%
}
\makeatother
\newcommand{\bigC}{\DOTSB\bigop[0.92]{\mathrm{C}}}
\begin{document}
[
\bigC_{\subalign{i&=1 \ j&=i+1}}^{\subalign{j&=N \ i&=N-1}} t_it_j
\quad
\sum_{\subalign{i&=1 \ j&=i+1}}^{\subalign{j&=N \ i&=N-1}} t_it_j
]
\end{document}

A comparison between the present solution (top) and the one in https://tex.stackexchange.com/a/691911/4427 but with \larger[4] (bottom).

How to write an arbitrary Math symbol larger like summation?

2 Answers2