# Align equal signs while including text over equalities

I understand how to align multiple equations, but how can I do this if I want to also have text over the equalities. For example: It bugs me that the equal signs are no longer aligned. Here is my LaTeX:

\begin{align} p(\textbf{x} \mid \mathcal{D}, \alpha) &= \int p(\textbf{x} \mid \boldsymbol{\theta}) p(\boldsymbol{\theta} \mid \mathcal{D}, \alpha) \text{d} \boldsymbol{\theta} \\ &\stackrel{\text{Eq 4}}{=} \int p(\textbf{x} \mid \boldsymbol{\theta}) p(\boldsymbol{\theta} \mid \alpha') \text{d} \boldsymbol{\theta} \\ &= p(\textbf{x} \mid \alpha'). \tag{5} \end{align}


Is there a solution to this?

• Off-topic: Encasing an align environment inside $$...$$ cannot possibly work correctly -- at least not as a LaTeX document. Please be more precise about you actually do. – Mico Apr 16 at 18:47
• Fair point. I'm technically using MathJax, which requires this to work, but I should have edited it for the post. – gwg Apr 16 at 20:34
• MathJax (used on this site) works with align without . – Bernard Apr 16 at 20:39

Here I use \mathclap to insure that the overstack takes up zero horizontal space.

Also, change the \textbf instances to \mathbf (thanks, Mico).

Finally, ditch the  delimiters. \documentclass{article} \usepackage{mathtools} \begin{document} \begin{align} p(\mathbf{x} \mid \mathcal{D}, \alpha) &= \int p(\mathbf{x} \mid \boldsymbol{\theta}) p(\boldsymbol{\theta} \mid \mathcal{D}, \alpha) \text{d} \boldsymbol{\theta} \\ &\stackrel{\mathclap{\text{Eq 4}}}{=} \int p(\mathbf{x} \mid \boldsymbol{\theta}) p(\boldsymbol{\theta} \mid \alpha') \text{d} \boldsymbol{\theta} \\ &= p(\mathbf{x} \mid \alpha'). \tag{5} \end{align} \end{document} A simple \makebox[0pt]{...} will solve the probl. Unrelated: do not nest align inside  ... $$ – and don't use the plain TeX construct ˆˆ ...$$ as it will yield incorrect spacing in LaTeX.

\documentclass{article}
\usepackage{amsmath}

\begin{document}

\begin{align}
p(\textbf{x} \mid \mathcal{D}, \alpha)
&= \int p(\textbf{x} \mid \boldsymbol{\theta}) p(\boldsymbol{\theta} \mid \mathcal{D}, \alpha) \text{d} \boldsymbol{\theta}
\\
&\stackrel{\text{\makebox[0pt]{Eq 4}}}{=} \int p(\textbf{x} \mid \boldsymbol{\theta}) p(\boldsymbol{\theta} \mid \alpha') \text{d} \boldsymbol{\theta}
\\
&= p(\textbf{x} \mid \alpha'). \tag{5}
\end{align}

\end{document} 