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Trajectory line plots in ggplot2

Source: R/traj_trajMap.R
trajMapStatic.Rd

[Experimental]

This function plots back trajectories using ggplot2. The function requires that data are imported using openair::importTraj(). It is a ggplot2 implementation of openair::trajPlot() with many of the same arguments, which should be more flexible for post-hoc changes.

Usage

trajMapStatic(
  data,
  colour = "height",
  type = NULL,
  group = NULL,
  size = NULL,
  linewidth = size,
  longitude = "lon",
  latitude = "lat",
  npoints = 12,
  xlim = NULL,
  ylim = NULL,
  crs = sf::st_crs(3812),
  origin = TRUE,
  map = TRUE,
  map.fill = "grey85",
  map.colour = "grey75",
  map.alpha = 0.8,
  map.lwd = 0.5,
  map.lty = 1,
  facet = NULL,
  ...
)

Arguments

data

A data frame containing a HYSPLIT trajectory, perhaps accessed with openair::importTraj().

required

A data frame containing HYSPLIT model outputs. If this data were not obtained using openair::importTraj().

colour

Data column to map to the colour of the trajectories.

default: NULL

This column may be numeric, character, factor or date(time). This will commonly be a pollutant concentration which has been joined (e.g., by dplyr::left_join()) to the trajectory data by "date". The scale can be edited after the fact using ggplot2::scale_color_continuous() or similar.

type

A method to condition the data for separate plotting.

default: NULL

Used for splitting the trajectories into different groups which will appear as different panels. Passed to openair::cutData().

group

Column to use to distinguish different trajectory paths.

default: NULL

By default, trajectory paths are distinguished using the arrival date. group allows for additional columns to be used (e.g., "receptor" if multiple receptors are being plotted).

size, linewidth

Data column to map to the size/width of the trajectory marker/paths, or absolute size value.

default: NULL

Similar to the colour argument, this defines a column to map to the size of the circular markers or the width of the paths. These scales can be edited after the fact using ggplot2::scale_size_continuous(), ggplot2::scale_linewidth_continuous(), or similar. If numeric, the value will be directly provided to ggplot2::geom_point(size = ) or ggplot2::geom_path(linewidth = ).

latitude, longitude

The decimal latitude/longitude.

default: "lat" / "lon"

Column names representing the decimal latitude and longitude.

npoints

Interval at which points are placed along the trajectory paths.

default: 12

A dot is placed every npoints along each full trajectory. For hourly back trajectories points are plotted every npoints hours. This helps to understand where the air masses were at particular times and get a feel for the speed of the air (points closer together correspond to slower moving air masses). Defaults to 12.

xlim, ylim

The x- and y-limits of the plot.

default: NULL

A numeric vector of length two defining the x-/y-limits of the map, passed to ggplot2::coord_sf(). If NULL, limits will be estimated based on the lat/lon ranges of the input data.

crs

The coordinate reference system (CRS) into which all data should be projected before plotting.

default: sf::st_crs(3812)

This argument defaults to the Lambert projection, but can take any coordinate reference system to pass to the crs argument of ggplot2::coord_sf(). Alternatively, crs can be set to NULL, which will typically render the map quicker but may cause countries far from the equator or large areas to appear distorted.

origin

Draw the receptor point as a circle?

default: TRUE

When TRUE, the receptor point(s) are marked with black circles.

map

Draw a base map?

default: TRUE

Draws the geometries of countries under the trajectory paths.

map.fill

Colour to use to fill the polygons of the base map.

default: "grey85"

See colors() for colour options. Alternatively, a hexadecimal color code can be provided.

map.colour

Colour to use for the polygon borders of the base map.

default: "grey75"

See colors() for colour options. Alternatively, a hexadecimal color code can be provided.

map.alpha

Transparency of the base map polygons.

default: 0.8

Must be between 0 (fully transparent) and 1 (fully opaque).

map.lwd

Line width of the base map polygon borders.

default: 0.5

Any numeric value.

map.lty

Line type of the base map polygon borders.

default: 1

See ggplot2::scale_linetype() for common examples. The default, 1, draws solid lines.

facet

Deprecated. Please use type.

...

Arguments passed on to openair::cutData

names

By default, the columns created by cutData() are named after their type option. Specifying names defines other names for the columns, which map onto the type options in the same order they are given. The length of names should therefore be equal to the length of type.

suffix

If name is not specified, suffix will be appended to any added columns that would otherwise overwrite existing columns. For example, cutData(mydata, "nox", suffix = "_cuts") would append a nox_cuts column rather than overwriting nox.

hemisphere

Can be "northern" or "southern", used to split data into seasons.

n.levels

Number of quantiles to split numeric data into.

start.day

What day of the week should the type = "weekday" start on? The user can change the start day by supplying an integer between 0 and 6. Sunday = 0, Monday = 1, ... For example to start the weekday plots on a Saturday, choose start.day = 6.

is.axis

A logical (TRUE/FALSE), used to request shortened cut labels for axes.

local.tz

Used for identifying whether a date has daylight savings time (DST) applied or not. Examples include local.tz = "Europe/London", local.tz = "America/New_York", i.e., time zones that assume DST. https://en.wikipedia.org/wiki/List_of_zoneinfo_time_zones shows time zones that should be valid for most systems. It is important that the original data are in GMT (UTC) or a fixed offset from GMT.

latitude,longitude

The decimal latitude and longitudes used when type = "daylight". Note that locations west of Greenwich have negative longitudes.

Value

a ggplot2 plot

See also

openair::trajPlot()

trajMap() for the interactive leaflet equivalent of trajMapStatic()

Other static trajectory maps: trajLevelMapStatic()

Examples

if (FALSE) { # \dontrun{
# colour by height
trajMapStatic(traj_data) +
  ggplot2::scale_color_gradientn(colors = openair::openColours())

# colour by PM10, log transform scale
trajMapStatic(traj_data, colour = "pm10") +
  ggplot2::scale_color_viridis_c(trans = "log10") +
  ggplot2::labs(color = openair::quickText("PM10"))

# color by PM2.5, lat/lon projection
trajMapStatic(traj_data, colour = "pm2.5", crs = sf::st_crs(4326)) +
  ggplot2::scale_color_viridis_c(option = "turbo") +
  ggplot2::labs(color = openair::quickText("PM2.5"))
} # }