Strikeout formula inside eqnarray?

Question

I want to strikeout a part of my paper. In particular, this one:

When bla bla $s$ bla bla $v$, bla bla $\boldsymbol{x}_{v}$, bla bla, the equation is:
\begin{eqnarray}
\displaystyle p_{v,s} & = & \displaystyle v+s = \nonumber\\
& = & \displaystyle  v^{2} - s^{3}. \label{eqn:pvs}
\end{eqnarray}

I've tried with \cancel but this only works with the first part of the text:

\cancel{When bla bla $s$ bla bla $v$, bla bla $\boldsymbol{x}_{v}$, bla bla, the equation is:}

and I get error when I use it on eqnarray. I've also tried \sout but the result was the same.

Additions

This is what I get when I use \sout on the text part. I would like that also the equation is stricken out!

Answer 1

It is not possible to directly span a \cancel or \sout across the alignment points & since each "cell" forms a group. That is, you want to start inside one group and span across to another group. One way around this might be to use tikzmark to remember left/right nodes inside a display, or overlay the strikeout after the fact. I've chosen to do the latter here:

\documentclass{article}
\usepackage{amsmath,ulem}% http://ctan.org/pkg/{amsmath,ulem}
\begin{document}
\sout{When bla bla~$s$ bla bla~$v$, bla bla~$\boldsymbol{x}_v$, bla bla, the equation is:}
\begin{align}
  p_{v,s} &= v + s\llap{\sout{\phantom{$p_{v,s} = v + s$}}} \nonumber \\
          &= v^2 - s^3.\llap{\sout{\phantom{$= v^2 - s^3.$}}} \label{eqn:pvs}
\end{align}
\end{document}

The idea is to set the equation as-is and then (at the end of each row/line) insert a zero-width left overlap where you \sout (or \cancel) the same equation. Using \phantom gives you the correct spacing without re-setting the content.

If you use the same approach using eqnarray, you'll obtain an incorrect layout, since eqnarray doesn't provide the correct spacing around the aligned item.