2

Edited

I am having trouble using the alignenvironment, which I've read is a better alternative to eqnarrayto align equations.

Hereafter I display the PDF output of my Latex code:

Output

I would like the max to be aligned with the \forall:

enter image description here

The code that I've written is the following:

\begin{align*}
\max_{\lambda,\lambda_0} M
\\
\forall i \in \{1,...,n\}, &\; \frac{y_i f(\mathbf{x}_i)}{\|\vec{\lambda}\|} \geq M 
\\
&\; \Leftrightarrow y_i \left(\frac{\vec{\lambda}^{\:T} \mathbf{x}_i+\lambda_0}{\|\vec{\lambda}\|}\right) \geq M 
\end{align*}

Would someone kindly point out what am I getting wrong?

3
  • Welcome to TeX.SX! Please don't post code as pictures, it's really annoying for those that might want to test the code. Copy the code into the question. – Torbjørn T. May 4 '16 at 13:40
  • Do you mean vertically aligned? – Bernard May 4 '16 at 13:45
  • Indeed, vertically aligned. – Daneel Olivaw May 4 '16 at 13:47
3

The following solution nests an aligned environment inside an align* environment.

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{align*}
&\max_{\lambda,\lambda_0} M\\
&\,\forall i \in \{1,\dots,n\}, 
  \begin{aligned}[t]
    &\frac{y_i f(\mathbf{x}_i)} {\|\vec{\lambda}\|} \geq M \\
    &\Leftrightarrow y_i \biggl(\frac{\vec{\lambda}^{\:T} 
        \mathbf{x}_i+\lambda_0}{\|\vec{\lambda}\|}\biggr) \geq M
  \end{aligned}
\end{align*}
\end{document}
3
  • The issue with this solution is that the first fraction is no longer aligned with the \Leftrightarrow. I would like two vertical alignments: 1) \max aligned with \forall and 2) the first fraction aligned with \Leftrightarrow. – Daneel Olivaw May 4 '16 at 14:03
  • Ok the edited version also works, thank you. – Daneel Olivaw May 4 '16 at 14:09
  • @DaneelOlivaw - When I posted the first version of my answer, I hadn't noticed yet that you'd edited your posting in the meantime. Once I saw the new version, I updated my answer accordingly... – Mico May 4 '16 at 14:17
3

Maybe this is the desired output:

documentclass{article}
\usepackage{amsmath}

\begin{document}

\begin{alignat*}{2}
&\! % or \max would be a bit to the right
\max_{\lambda,\lambda_0} M
\\
&\forall i \in \{1,\dots,n\},
&&\frac{y_i f(\mathbf{x}_i)}{\|\vec{\lambda}\|} \geq M
\\
&& \Leftrightarrow {} &
  y_i \left(\frac{\vec{\lambda}^{\,T}
  \mathbf{x}_i+\lambda_0}{\|\vec{\lambda}\|}\right) \geq M
\end{alignat*}

\end{document}

enter image description here

2
  • Ok yes, this is what I was looking for - just changing places of the third & and \Leftrightarrow. Thank you. By the way, what is the purpose of the empty brackets situated at the right of \Leftrightarrow? – Daneel Olivaw May 4 '16 at 14:07
  • @DaneelOlivaw Spacing. – egreg May 4 '16 at 14:19

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