equationsmath-modenumbering
I want to manually label equation number ? For example I want to label this equation 3.1 instead of (1) which automatically pops up. Is it also possible in split environment as well or not ?
\begin{equation}
\log \mu_{ijk}= \lambda + \lambda_i ^I + \lambda_j ^J+\lambda_k ^K+\lambda_{ij} ^{IJ}+\lambda_{ik} ^{IK}+\lambda_{jk} ^{JK}+\lambda_{ijk} ^{IJK} \label{eq:3.1}
\end{equation}
Assuming that these numbered quote environments are at the top level and not nested in other list environments, you can exploit the fact that, unless your equation numbers are too wide, they will fit in the available white space; in case they are wider for fitting, you should redefine quote in the first place.
\documentclass{article}
\usepackage{blindtext}
\newsavebox\ideabox
\newenvironment{idea}
{\begin{equation}
\begin{lrbox}{\ideabox}
\begin{minipage}{\dimexpr\columnwidth-2\leftmargini}
\setlength{\leftmargini}{0pt}%
\begin{quote}}
{\end{quote}
\end{minipage}
\end{lrbox}\makebox[0pt]{\usebox{\ideabox}}
\end{equation}}
\begin{document}
\begin{quote}\blindtext\end{quote}\begin{equation}E=mc^2\end{equation}
\begin{idea}
\blindtext
\end{idea}
\end{document}
The “equationed” quote is typeset in a zero width box, so the equation number will not force a shift to the left.
Use a single column array:
\documentclass[]{article}
\usepackage{amsmath}
\usepackage{multicol}
\newcommand{\tsub}[1]{_{\mathrm{#1}}}
\begin{document}
\begin{multicols*}{2}
Using Poisson's equation for gravity,
\begin{equation} \label{eq: phi}
\Phi(r) =
\left\{
\begin{array}{@{}r@{}}
\dfrac{GM\tsub{tot}}{R\tsub{vir}}
\biggl[\ln\biggl(\frac{r}{R\tsub{vir}}\biggr) - 1\biggr]
\\
r < R\tsub{vir}
\\[2ex]
\dfrac{-GM\tsub{tot}}{r} \hfill r > R\tsub{vir} .
\end{array}
\right.
\end{equation}
\end{multicols*}
\end{document}
Textual subscripts should be in upright type and so I set them.
On the other hand, with the twocolumn option the text width is wider and you can use a better way.
\documentclass[twocolumn]{article}
\usepackage{amsmath,mathtools}
\newcommand{\tsub}[1]{_{\mathrm{#1}}}
\begin{document}
Using Poisson's equation for gravity,
\begin{equation} \label{eq: phi}
\Phi(r) =
\begin{dcases}
\dfrac{GM\tsub{tot}}{R\tsub{vir}}
\biggl[\ln\biggl(\frac{r}{R\tsub{vir}}\biggr) - 1\biggr]
&
r < R\tsub{vir}
\\
\dfrac{-GM\tsub{tot}}{r} & r > R\tsub{vir} .
\end{dcases}
\end{equation}
\end{document}
Best Answer
You can use
\tag: