geom_quiver: Quiver plots for ggplot2
In pbs-assess/gfranges: Groundfish Ranges

Description Usage Arguments Format Computed variables Examples

Displays the direction and length of vectors on a graph.

geom_quiver(
  mapping = NULL,
  data = NULL,
  stat = "quiver",
  position = "identity",
  center = FALSE,
  rescale = FALSE,
  vecsize = NULL,
  na.rm = FALSE,
  show.legend = NA,
  inherit.aes = TRUE,
  ...
)

GeomQuiver

stat_quiver(
  mapping = NULL,
  data = NULL,
  geom = "quiver",
  position = "identity",
  center = FALSE,
  rescale = FALSE,
  vecsize = NULL,
  na.rm = FALSE,
  show.legend = NA,
  inherit.aes = TRUE,
  ...
)

StatQuiver

`mapping`	Set of aesthetic mappings created by `aes()` or `aes_()`. If specified and `inherit.aes = TRUE` (the default), it is combined with the default mapping at the top level of the plot. You must supply `mapping` if there is no plot mapping.
`data`	The data to be displayed in this layer. There are three options: If `NULL`, the default, the data is inherited from the plot data as specified in the call to `ggplot()`. A `data.frame`, or other object, will override the plot data. All objects will be fortified to produce a data frame. See `fortify()` for which variables will be created. A `function` will be called with a single argument, the plot data. The return value must be a `data.frame`, and will be used as the layer data. A `function` can be created from a `formula` (e.g. `~ head(.x, 10)`).
`position`	Position adjustment, either as a string, or the result of a call to a position adjustment function.
`center`	If `FALSE` (the default), the vector lines will start at the specified x and y. If `TRUE`, the arrows will be centered about x and y.
`rescale`	If `FALSE` (the default), the vectors will not be rescaled. If `TRUE`, the vectors given by (u, v) will be rescaled using the `scale` function.
`vecsize`	By default (NULL), vectors sizing is automatically determined. If a grid can be identified, they will be scaled to the grid, if not, the vectors will not be scaled. By specifying a numeric input here, the length of all arrows can be adjusted. Setting vecsize to zero will prevent scaling the arrows.
`na.rm`	If `FALSE` (the default), removes missing values with a warning. If `TRUE` silently removes missing values.
`show.legend`	logical. Should this layer be included in the legends? `NA`, the default, includes if any aesthetics are mapped. `FALSE` never includes, and `TRUE` always includes. It can also be a named logical vector to finely select the aesthetics to display.
`inherit.aes`	If `FALSE`, overrides the default aesthetics, rather than combining with them. This is most useful for helper functions that define both data and aesthetics and shouldn't inherit behaviour from the default plot specification, e.g. `borders()`.
`...`	Other arguments passed on to `layer()`. These are often aesthetics, used to set an aesthetic to a fixed value, like `colour = "red"` or `size = 3`. They may also be parameters to the paired geom/stat.
`geom`	The geometric object to use display the data

An object of class GeomQuiver (inherits from GeomSegment, Geom, ggproto, gg) of length 2.

An object of class StatQuiver (inherits from Stat, ggproto, gg) of length 3.

x: centered x start position for velocity arrow
y: centered y start position for velocity arrow
xend: centered x end position for velocity arrow
yend: centered y end position for velocity arrow

library(ggplot2)
# Quiver plots of mathematical functions
expand.grid(x = seq(0, pi, pi / 12), y = seq(0, pi, pi / 12)) %>%
  ggplot(aes(x = x, y = y, u = cos(x), v = sin(y))) +
  geom_quiver()

# Removing automatic scaling
ggplot(seals, aes(x = long, y = lat, u = delta_long, v = delta_lat)) +
  geom_quiver(vecsize = NULL) +
  borders("state")
## Not run: 
# Centering arrows is useful for plotting on maps.
library(dplyr)
library(ggmap)
wind_data <- wind %>% filter(between(lon, -96, -93) & between(lat, 28.7, 30))
qmplot(lon, lat, data = wind_data, extent = "panel", geom = "blank", zoom = 8, maptype = "toner-lite") +
  geom_quiver(aes(u = delta_lon, v = delta_lat, colour = spd), center = TRUE)

## End(Not run)