Math & Science ⇒ Align equation to signal

[marcoesteves]

Hello, is it possible align an equation at main signal?

E.g. I'd like to align this equation at equal signal

Code: Select all

\begin{equation}
\begin{array}{c}
\begin{aligned}
 {V^\pi }(s) = {E_\pi }\left\{ {{R_k}|{s_k} = s} \right\} \\ 
  = {E_\pi }\left\{ {{r_{k + 1}} + \gamma \sum\limits_{l = 0}^\infty  {{\gamma ^l}{r_{k + l + 2}}|{s_k} = s} } \right\} \\ 
  = \sum\limits_a^{} {\pi (s,a)\sum\limits_{s'}^{} {P_{ss'}^a\left[ {R_{ss'}^a + \gamma {E_\pi }\left\{ {\sum\limits_{l = 0}^\infty  {{\gamma ^l}{r_{t + l + 2}}|{s_{k + 1}} = s'} } \right\}} \right]} }  \\ 
  = \sum\limits_a^{} {\pi (s,a)\sum\limits_{s'}^{} {P_{ss'}^a\left[ {R_{ss'}^a + \gamma {V^\pi }(s')} \right]} }  \\ 
 \end{aligned}
 \end{array}
\end{equation}

[Stefan Kottwitz]

Which "signal" do you mean? Alignment can be done using the & symbol inside aligned and other amsmath environments. Your description is not clear to me.

Stefan

[marcoesteves]

Which "signal" do you mean? Alignment can be done using the & symbol inside aligned and other amsmath environments. Your description is not clear to me.

Stefan

Sorry! Align at equal signal for example. It's nicier than right align.

[Stefan Kottwitz]

That could be done easily, I've just inserted some & symbols like mentioned above, each & right before the equal sign:

Code: Select all

\begin{equation}
\begin{array}{c}
\begin{aligned}
{V^\pi }(s) &= {E_\pi }\left\{ {{R_k}|{s_k} = s} \right\} \\
  &= {E_\pi }\left\{ {{r_{k + 1}} + \gamma \sum\limits_{l = 0}^\infty  {{\gamma ^l}{r_{k + l + 2}}|{s_k} = s} } \right\} \\
  &= \sum\limits_a^{} {\pi (s,a)\sum\limits_{s'}^{} {P_{ss'}^a\left[ {R_{ss'}^a + \gamma {E_\pi }\left\{ {\sum\limits_{l = 0}^\infty  {{\gamma ^l}{r_{t + l + 2}}|{s_{k + 1}} = s'} } \right\}} \right]} }  \\
  &= \sum\limits_a^{} {\pi (s,a)\sum\limits_{s'}^{} {P_{ss'}^a\left[ {R_{ss'}^a + \gamma {V^\pi }(s')} \right]} }  \\
\end{aligned}
\end{array}
\end{equation}

Here's an alternative way using split instead of array and aligned:

Code: Select all

\begin{equation}
\begin{split}
{V^\pi }(s) &= {E_\pi }\left\{ {{R_k}|{s_k} = s} \right\} \\
  &= {E_\pi }\left\{ {{r_{k + 1}} + \gamma \sum\limits_{l = 0}^\infty  {{\gamma ^l}{r_{k + l + 2}}|{s_k} = s} } \right\} \\
  &= \sum\limits_a^{} {\pi (s,a)\sum\limits_{s'}^{} {P_{ss'}^a\left[ {R_{ss'}^a + \gamma {E_\pi }\left\{ {\sum\limits_{l = 0}^\infty  {{\gamma ^l}{r_{t + l + 2}}|{s_{k + 1}} = s'} } \right\}} \right]} }  \\
  &= \sum\limits_a^{} {\pi (s,a)\sum\limits_{s'}^{} {P_{ss'}^a\left[ {R_{ss'}^a + \gamma {V^\pi }(s')} \right]} }  \\
\end{split}
\end{equation}

Stefan

[marcoesteves]

Thank you very much.

& char defines where the "alignment" should be done.