nc <- sf::st_read(system.file("shape/nc.shp", package = "sf"), quiet = TRUE)
vplot(nc) |>
mark_sf(fill = BIR74) |>
scale_fill_binned(style = "quantile", n = 6, palette = "Batlow") |>
coord_sf()
Most of vellumplot maps columns of a data frame to x and y. Two important data shapes do not fit that mould: spatial geometries, where the coordinates live in a geometry column and the aspect ratio matters, and graphs, where the positions have to be computed by a layout algorithm first. vellumplot handles both with the same grammar, through entry points suited to each data type.
Maps from sf
mark_sf() draws the geometry column of an sf object. Points, lines, and polygons each render appropriately, and there are no x/y encodings: the coordinates come from the geometry. Other aesthetics map feature attributes as usual, so fill = AREA gives you a choropleth. Pair it with coord_sf(), which reprojects every layer to a common CRS before training and locks the map aspect ratio so nothing is stretched.
Because mark_sf() is an ordinary layer, you can stack it: draw a base layer of boundaries, then a second mark_sf() for highlighted features or point locations on top, and every layer reprojects together.
Networks from igraph
vgraph() starts a node-link diagram from an igraph graph. It runs a layout (stress majorization by default, via graphlayouts) and produces a spec whose node and edge tables already carry the x, y, xend, yend, and name columns the graph marks need. Then mark_edges() and mark_nodes() draw it. Draw order is fixed no matter how you pipe them: edges below nodes below labels.
g <- igraph::make_graph("Zachary")
g <- igraph::set_vertex_attr(
g, "grp",
value = as.factor(igraph::cluster_louvain(g)$membership)
)
g <- igraph::set_vertex_attr(g, "deg", value = igraph::degree(g))
vgraph(g, layout = "stress") |>
mark_edges(alpha = 0.4) |>
mark_nodes(size = deg, fill = grp) |>
scale_size(range = c(2, 9))
The node and edge aesthetics are the same ones you already know. mark_nodes() takes size, shape, fill, and color; mark_edges() takes color, linewidth (scaled by scale_edge_width()), and alpha, plus arrow = TRUE for directed graphs. mark_node_text() adds vertex labels.
vgraph(g, layout = "stress") |>
mark_edges(color = "grey70") |>
mark_nodes(fill = grp, size = 6) |>
mark_node_text(label = name, size = 8)
Choosing a layout
layout accepts a name ("stress", "sparse_stress", "backbone", "fr", "kk", "circle", "tree", "sugiyama", and more), a supplied N-by-2 coordinate matrix, or a function that returns one. Stochastic layouts take a seed so the figure is reproducible.
vgraph(g, layout = "circle") |>
mark_edges(alpha = 0.3) |>
mark_nodes(fill = grp, size = 5)
Both of these are still ordinary specs. They face the same scales, themes, and composition tools as any other plot, and they render to a file with render_plot(). For per-feature interactivity (tooltips and data keys on map features or nodes), see the interactivity notes on mark_sf() and the mark reference pages.