An alternative API and specification to tidy_dagitty(), as_tidy_dagitty()
allows you to create tidy_dagitty objects from data frames. There is also a
method for dagitty objects, which is a thin wrapper for tidy_dagitty().
To create a DAG from a data frame, it must contain name and to columns,
representing the nodes and any edges leading from the nodes. If there are
x, y, xend, and yend columns, they will be used as coordinates.
Otherwise, layout will be used. See tidy_dagitty for more information
about layouts. Additionally, you can specify status (one of exposure,
outcome, or latent) by including a status column. Any other columns in
the data set will also be joined to the tidy_dagitty data.