# align, aligned and R Markdown

I have been working in R Markdown, which supports LaTeX, including in display mode. I had the following snippet for displaying aligned equations

\begin{align} a_1 &= \beta_0 \\ b_1 &= \beta_1 \\ c_1 &= \beta_2 \\ d_1 &= \beta_3 \end{align}


This worked great for me when I chose to output as HTML. I believe this uses MathJax.

However, when I changed the output format to PDF, I get the following error message:

processing file: dummy.Rmd output file: dummy.knit.md

! Package amsmath Error: Erroneous nesting of equation structures; (amsmath) trying to recover with aligned'.

See the amsmath package documentation for explanation. Type H for immediate help. ...

l.87 \end{align}

pandoc: Error producing PDF from TeX source Error: pandoc document conversion failed with error 43 Execution halted

When I change this to use aligned instead of align, it works with both.

This is an entire .Rmd file that shows the problem:

---
title: "dummy"
author: "Harold Ship"
date: "23 December 2015"
output: pdf_document
---

\begin{align} a_1 &= \beta_0 \\ b_1 &= \beta_1 \\ c_1 &= \beta_2 \\ d_1 &= \beta_3 \end{align}


My question is, what is the difference between align and aligned, and why does align not work here with pandoc?

• Welcome to TeX.SX! We have this question a lot of times. align is a full math environment, which must not be enclosed within (the deprecated!)  form or . aligned on the other hand requires to appear in a math-mode enabling environment. I don't know why mathjax does allow this syntax, but pandoc uses LaTeX externally (as far as I know) and the error is reported. – user31729 Dec 24 '15 at 7:29 • What does the R Markdown code look like to achieve the LaTeX output you show? – Werner Dec 24 '15 at 7:50 ## 1 Answer So, just to be clear (as it says this is unanswered), just write the align (without ):

\begin{align}
a_1 &= \beta_0 \\
b_1 &= \beta_1 \\
c_1 &= \beta_2 \\
d_1 &= \beta_3
\end{align}


and not

\begin{align} a_1 &= \beta_0 \\ b_1 &= \beta_1 \\ c_1 &= \beta_2 \\ d_1 &= \beta_3 \end{align}
`