matrix by matrix in R markdown

Question

I want to have multiple matrices side by side to present spectral decomposition in R markdown, but it doesn't seem to work. Please help

$$
\left(\begin{array}
0.8944272 & 0.4472136\\
-0.4472136 & -0.8944272
\end{array}\right\)

\left(\begin{array}
10 & 0\\
0 & 5
\end{array}\right)
$$ 

Answer 1

Three minor corrections should be sufficient to make this work for both, HTML and PDF output:

1. remove the backslash before the closing bracket in \right\)
2. delete the empty line in the middle
3. specify the column alignment in each array environment, e.g., with \begin{array}{cc}

-

$$
\left(\begin{array}{cc} 
0.8944272 & 0.4472136\\
-0.4472136 & -0.8944272
\end{array}\right)
\left(\begin{array}{cc} 
10 & 0\\ 
0 & 5
\end{array}\right)
$$ 

Answer 2

You can also use the *matrix environments of amsmath

$$
\begin{pmatrix}
0.8944272 & 0.4472136\\
-0.4472136 & -0.8944272
\end{pmatrix}
\begin{pmatrix}
10 & 0\\ 
0 & 5
\end{pmatrix}
$$

amsmath is supported by Pandoc and MathJax, the tools that are commonly used when converting RMarkdown to HTML or PDF.

Answer 3

You can also do this to get brackets instead of parentheses

$\left[\begin{array}{ccc}
10 & 0\\
0 & 5
\end{array}\right]$