# Make equation number in middle with left alignment in latex

I need to place the following bulk of equation to left alignment with keeping the equation number in the middle, however using flalign require set option on/off by line for equation number which at last will not be in the middle.

 \begin{flalign}
\ell_1(\bm{\phi})& =\sum_{i=1}^{N-N^*} \sum_{j=2}^{d_i-1} ln(1-
\bm{P}_{ij}),&\nonumber\\
\ell_2(\bm{\phi})& =\sum_{i=1}^{N-N^*} ln\,\bm{P}_{id_i},&
\end{flalign}


On the other hand, when using aligned with equation, equation number will be in the middle but the whole bulk of equation moved to center.

\begin{aligned} \ell_1(\bm{\phi})& =\sum_{i=1}^{N-N^*} \sum_{j=2}^{d_i-1} ln(1- \bm{P}_{ij}),\\ \ell_2(\bm{\phi})& =\sum_{i=1}^{N-N^*} ln\,\bm{P}_{id_i}, \end{aligned}


How can I keep the equation left aligned with equation number in the middle.

It's not clear why a particular equation should be left aligned. If you want all equations to be left aligned, use the fleqn option.

Anyway, here's a way with flalign.

Function names such as “ln”, “sin”, “exp” should be typed in with a backslash: \ln and so on; this will give the correct spacing, besides using upright font shape.

\documentclass{article}
\usepackage{amsmath,bm}

\usepackage[nopar]{lipsum} % for context

\begin{document}

\lipsum[4]
\begin{flalign}
& \begin{aligned}
\ell_1(\bm{\phi})& =\sum_{i=1}^{N-N^*} \sum_{j=2}^{d_i-1} \ln(1-\bm{P}_{ij}),\\
\ell_2(\bm{\phi})& =\sum_{i=1}^{N-N^*} \ln\bm{P}_{id_i},
\end{aligned}
&&
\end{flalign}
\lipsum[4]

\end{document}


• I know that setting fleqn as option in the document class make all equation left alignment, however I just want them left alignment only in the proof appendix while all equation in all the thesis are in center alignment. However, I use your suggested solution by using flalign with aligned and it worked perfectly. – N. I. ElZayat Dec 18 '18 at 10:49

Do note that the left-hand shift of the first set of equations is not caused by the use of flalign, per se. Instead, the shift is caused by the presence of additional & symbols.

To shift a nested equation/aligned system to the left, all you need to do is insert the instruction

\hspace*{6cm}\null  % choose offset amount suitably


between \end{aligned} and .

Oh, and do please write \ln rather than just ln to denote the natural logarithm operator.

\documentclass{article}
\usepackage{amsmath,bm}
\begin{document}
\begin{aligned} \ell_1(\bm{\phi}) &= \sum_{i=1}^{N-N^*} \sum_{j=2}^{d_i-1} \ln(1-\bm{P}_{ij}),\\ \ell_2(\bm{\phi}) &= \sum_{i=1}^{N-N^*} \ln\bm{P}_{id_i}, \end{aligned}\hspace*{6cm}\null % choose offset amount suitably
\end{document}

• You won for 35 seconds :-) Excellent and congratulations on your response. – Sebastiano Dec 18 '18 at 9:57
• Your solution also work perfect with me – N. I. ElZayat Dec 18 '18 at 11:16

You can use the fleqn environment from nccmath, which makes equations in the environment start at a fixed distance of the left margin via an optional argument (default 0pt):

\documentclass{article}
\usepackage{showframe}
\renewcommand{\ShowFrameLinethickness}{0.3pt}
\usepackage{amsmath, bm, nccmath}

\begin{document}

\begin{fleqn}[1em]
\begin{aligned} \ell_1(\bm{\phi})& =\sum_{i=1}^{N-N^*} \sum_{j=2}^{d_i-1} \ln(1- \bm{P}_{ij}),\\ \ell_2(\bm{\phi})& =\sum_{i=1}^{N-N^*} \ln\,\bm{P}_{id_i}, \end{aligned}
\end{fleqn}

\end{document}


• Oh! yes. Actually I didn't what the O.P. had written. Thanks! – Bernard Dec 18 '18 at 10:10

You could, alternatively use, \usepackage{empheq}. Here I have added a picture of the differents environment (see the table) that you can use:

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\documentclass{article}
\usepackage{empheq}
\usepackage{amsmath}
\usepackage{bm}
\begin{document}

\begin{empheq}{flalign}
\begin{aligned}
\ell_1(\bm{\phi})& =\sum_{i=1}^{N-N^*} \sum_{j=2}^{d_i-1} \ln(1-
\bm{P}_{ij}),\\
\ell_2(\bm{\phi})& =\sum_{i=1}^{N-N^*} \ln\,\bm{P}_{id_i},
\end{aligned}&&
\end{empheq}

\end{document}

• In fact this package does not work with me. The equation still appears in center alignment. – N. I. ElZayat Dec 18 '18 at 10:51
• Your LaTeX distribution will probably not be updated. Try to check the date of your version. – Sebastiano Dec 18 '18 at 10:59
• It seems that you'r right I will check for an update. – N. I. ElZayat Dec 18 '18 at 11:13
• @ samcarter I did not update I used one solution of the suggested above and it works great with me – N. I. ElZayat Dec 18 '18 at 13:28