Add Vector Field Layers to Ggplots.

ggfields

Overview

Add vector field layers to your ggplot2::ggplot(). Although it has similarities with ggplot2::geom_spoke(), ggfields offers some distinct features:

• The radius aesthetic is mapped to a scale and therefore can be added to the guides (see vignette("radius_aes")).
• Not only data.frames are supported, but also geometric data (sf::st_sf() and stars::st_as_stars()).
• Corrects angles for displayed aspect ratio or coordinate system (see vignette("angle_correction")).

Installation

Get CRAN version

install.packages("ggfields")

Get development version from r-universe

install.packages("ggfields", repos = c("https://pepijn-devries.r-universe.dev", "https://cloud.r-project.org"))

Adding vector fields to a map

The example below shows how seawater current data can be added to a map:

library(ggplot2)
library(ggfields)
library(ggspatial) ## For annotating with Open Street Map

data(seawatervelocity)

ggplot() +
  ggspatial::annotation_map_tile(
    alpha      = 0.25,
    cachedir   = tempdir()) +
  geom_fields(
    data       = seawatervelocity,
    aes(radius = as.numeric(v),
        angle  = as.numeric(angle),
        colour = as.numeric(v)),
    max_radius = grid::unit(0.7, "cm")) +
  labs(colour  = "v[m/s]",
       radius  = "v[m/s]") +
  scale_radius_binned() +
  scale_colour_viridis_b(guide = guide_bins())

Simple data.frames

Vector arrows can also be added to simple plots with x and y data:

## First generate some arbitrary data to plot:
n  <- 10
df <- data.frame(x = seq(0, 100, length.out = n), y = rnorm(n),
                 ang = seq(0, 2*pi, length.out = n))
df$len <- 2 + df$y + rnorm(n)/4

ggplot(df, aes(x = x, y = y)) +
  geom_line() +
  geom_fields(aes(angle = ang, radius = len), .angle_correction = NULL)