52

Here is my split equation:

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{equation}
\begin{split}
a_{ijk} =& \frac {Pr(M_{I} =2  \&  M_J=1 \& M_K =1 | I=i , J=j , K=k)}{Pr (M_I =1 \& M_J =1 \& M_K=1 | I=i , J=j)} \\
            =& \frac {\mu_{ijk211}}{\mu_{ijk111}}\\
\end{split}
\end{equation}
\end{document}

I want to align this equation to the left. Is this possible in an equation environment?

56

I would not use the equation environment; rather, I would use flalign as such:

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\noindent A \hfill Z
\begin{flalign}
a_{ijk} &= \frac {Pr(M_{I} =2  \&  M_J=1 \& M_K =1 | I=i , J=j , K=k)}{Pr (M_I =1 \& M_J =1 \& M_K=1 | I=i , J=j)}&&\\\nonumber
            &= \frac {\mu_{ijk211}}{\mu_{ijk111}}&&
\end{flalign}

\noindent A \hfill Z
\end{document}

Output

Another way to go is to set the fleqn option for the document class. However, this left-aligns all of your equations and hence should not be used when you want at least some equations to remain centered.

\documentclass[fleqn]{article}
\usepackage{amsmath}
\begin{document}
\noindent A \hfill Z
\begin{equation}
\begin{aligned}
a_{ijk} &= \frac {Pr(M_{I} =2  \&  M_J=1 \& M_K =1 | I=i , J=j , K=k)}{Pr (M_I =1 \& M_J =1 \& M_K=1 | I=i , J=j)}\\
            &= \frac {\mu_{ijk211}}{\mu_{ijk111}}\\
\end{aligned}
\end{equation}
\noindent A \hfill Z
\end{document}

For this output:

Output 2

As suggested by karlkoeller, if you want to get rid of the space between the left margin and the equation (to get a result similar to the first case), you should add \setlength{\mathindent}{0pt}. If you later want to indent it back to its default value, you can use the same command with a value of 15pt, which is the amount of pt a paragraph indent shifts its text to the right.

  • 7
    Or you could use the fleqn package option if you want all equations flush left. Eg: \usepackage[fleqn]{amsmath}. – Thruston Nov 18 '13 at 17:40
  • @Thruston I was just editing my answer to add this possibility! – Ludovic C. Nov 18 '13 at 17:40
  • @LudovicC. you might also swap "=&" round to "&=" which gives correct spacing around the relation. – Thruston Nov 18 '13 at 17:45
  • @Thruston Yes, true I was just copy/pasting the code from the OP, without checking that! – Ludovic C. Nov 18 '13 at 17:47
  • 1
    This did not result in a left-align for me. And yes, I included \usepackage{amsmath}. – user124384 Feb 7 '18 at 17:06
8

Note: This doesn't answer the question exactly. But still try this solution first as it is probably the simplest.

Use align, and put & at the beginning of every line. Use \\ to separate multiple equations.

\begin{align*}
& a_{ijk} = 2 \\
&(because ||V_1-V_2|| = \max_{i \in [d]}|V^i_1 - V^i_2|)
\end{align*}

(This works if you want to left align a set of equations, but the whole equations could be at the center if your equations are short)

  • Isn't this already covered by the accepted answer (flalign = align, but left-aligned as wanted by the OP)? – TeXnician Nov 9 '17 at 6:32
  • 1
    @TeXnician flalign is rarely used. The accepted answer didn't work for me. – Binu Jasim Nov 9 '17 at 6:36
  • flalign is commonly used if you do not want to pass fleqn as a documentclass option. And the OP's aim was to have equations flush left. – TeXnician Nov 9 '17 at 6:44
  • 1
    @TeXnician Fine. The reason why I added this answer is that this is the first answer googling "align equations left" gives. It doesn't answer OP exactly but still could be useful. – Binu Jasim Nov 9 '17 at 6:52
  • @TeXnician I would not delete the answer, because it indeed be an answer. Nevertheless it is a very ugly hack, I would not recommend to use. I think in such cases voting should be preferred to tell the users which suggestion should be used and which not. – Schweinebacke Nov 9 '17 at 8:44
2

Put & at the beginning of the line for left alignment and \\ at the end of the line to break line. Enclose the equation between \begin(split) and \end(split)

\begin{equation}
\begin{split}
&T_{eff}=\sum_{i=1}^n f_i.t_i \\
&=h_1t_1+(1-h_1)h_2t_2+(1-h_1)(1-h_2)h_3t_3+...+ \\
&(1-h_1)(1-h_2)...(1-h_{n-1})h_nt_n
\end{split}
\end{equation}
2

multline* did the trick for me

\begin{multline*}
p(x) = 3x^6 + 14x^5y + 590x^4y^2 + 19x^3y^3\\ 
- 12x^2y^4 - 12xy^5 + 2y^6 - a^3b^3
\end{multline*}
1

Note flalign requires at least two groups of alignment, whence a supplementary ampersand. I wanted to point another possibility with the fleqn environment from nccmath (which loads amsmath). This environment can take an optional argument to set the distance from the left margin the equation(s) start (default is 0 pt). It works somewhat like the subequations environment in the sense that all (groups of) equations inside the environment will start at the left margin.

\documentclass{article}
\usepackage{amsmath, nccmath}
\usepackage{geometry}

\begin{document}

Some text. Some more text. Some more text. Some more text. Some more text. Some more text. Some more text. Some more text. Some more text. Some more text. Some more text.

\begin{fleqn}[\parindent]
\begin{equation}
\begin{split}
a_{ijk} =& \frac {Pr(M_{I} =2 \& M_J=1 \& M_K =1 | I=i , J=j , K=k)}{Pr (M_I =1 \& M_J =1 \& M_K=1 | I=i , J=j)} \\
            =& \frac {\mu_{ijk211}}{\mu_{ijk111}}\\
\end{split}
\end{equation}
\end{fleqn}

\begin{equation}
\begin{split}
a_{ijk} =& \frac {Pr(M_{I} =2 \& M_J=1 \& M_K =1 | I=i , J=j , K=k)}{Pr (M_I =1 \& M_J =1 \& M_K=1 | I=i , J=j)} \\
            =& \frac {\mu_{ijk211}}{\mu_{ijk111}}\\
\end{split}
\end{equation}
\end{document}

\end{document} 

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