Add or update curvature for a single edge

curve_edge() sets the curvature for a single edge on a dagitty or tidy_dagitty object. Use set_curve_edges() to set multiple edges at once.

Usage

curve_edge(.dag, from, to, curvature = 0.3)

Arguments

.dag

A dagitty or tidy_dagitty object.

from

Character. The name of the source node.

to

Character. The name of the target node.

curvature

Numeric. The curvature value for the edge.

Value

The modified .dag object with updated curvature.

Curvature sign convention

Per-edge curvature is drawn by the ggarrow edge engine only. Set it with edge_engine = "ggarrow" on geom_dag() and the ggdag_*() quick plots, or globally with ggdag_options_set(edge_engine = "ggarrow"); the default ggraph engine draws every edge with the curvature of its own edge type and warns when it is handed a per-edge value it cannot draw.

ggarrow follows the grid::curveGrob() convention, so positive curvature curves below (to the right of) a left-to-right edge and negative curvature curves above it. ggdag passes the value through untouched.

A bidirected edge has no direction of its own, so ggdag draws it from the endpoint dagitty stores first. Naming its endpoints the other way round, as in curve_edge(dag, "y", "x", 0.5) for an edge stored as x <-> y, curves the edge to the same side of the page: the sign is flipped to match the direction the edge is drawn in.

Examples

dag <- dagify(y ~ x + m, m ~ x)
dag <- curve_edge(dag, from = "m", to = "y", curvature = 0.5)