For R Markdown, How do I display a matrix from R variable

Question

I have a rmd document where I have the following

```{r code_block, echo=FALSE}
A = matrix(c(1,3,0,1),2,2)
B = matrix(c(5,3,1,4),2,2)
```

$$
\\begin{bmatrix} 
1          


        

Answer 1

I figured out a function that plugs the numbers from the matrix into the correct LaTeX code. In the code block where you use it you need results='asis' to get the LaTeX to render, and you can wrap the function in writeLines along with the other parts you need.

I'm still open to more elegant solutions.

```{r}
A <- matrix(c(1, 3, 0, 1), 2, 2)
B <- matrix(c(5, 3, 1, 4), 2, 2)

# Utility function to print matrices in proper LaTeX format
print_mat <- function(mat) {
  n <- nrow(mat)
  c('\\begin{bmatrix}',
    paste0(sapply(seq_len(n - 1),
                  function(i) paste0(mat[i, ], collapse = ' & ')),
           ' \\\\'),
    paste0(mat[n, ], collapse = ' & '),
    '\\end{bmatrix}')
} 

```

```{r, results = 'asis'}
writeLines(c('$$',
             print_mat(A),
             '\\times',
             print_mat(B),
             '$$'))
```