Create matrices laying out the data in rows, similar to
`matrix(..., byrow = TRUE)`

, with a nicer-to-read syntax.
This is useful for small matrices, e.g. covariance matrices, where readability
is important. The syntax is inspired by `tribble()`

.

## Arguments

- ...
<

`dynamic-dots`

> Arguments specifying the structure of a`frame_matrix`

. Column names should be formulas, and may only appear before the data. These arguments are processed with`rlang::list2()`

and support unquote via`!!`

and unquote-splice via`!!!`

.

## Value

A matrix.