Pollution roses on dynamic and static maps

The pollroseMap() function creates a map using pollution roses as markers. Any number of pollutants can be specified using the pollutant argument, and multiple layers of markers can be created using type. By default, these maps are dynamic and can be panned, zoomed, and otherwise interacted with. Using the static argument allows for static images to be produced instead.

Usage

pollroseMap(
  data,
  pollutant = NULL,
  statistic = "prop.count",
  breaks = NULL,
  latitude = NULL,
  longitude = NULL,
  crs = 4326,
  type = NULL,
  popup = NULL,
  label = NULL,
  provider = "OpenStreetMap",
  cols = "turbo",
  alpha = 1,
  key = FALSE,
  legend = TRUE,
  legend.position = NULL,
  legend.title = NULL,
  legend.title.autotext = TRUE,
  control.collapsed = FALSE,
  control.position = "topright",
  control.autotext = TRUE,
  d.icon = 200,
  d.fig = 3.5,
  static = FALSE,
  static.nrow = NULL,
  progress = TRUE,
  ...,
  control = NULL
)

Arguments

data

Input data table with pollutant, wind, and geo-spatial information.

required | scope: dynamic & static

A data frame. The data frame must contain the data to plot the directional analysis marker, which includes wind speed (ws), wind direction (wd), and the column representing the concentration of a pollutant. In addition, data must include a decimal latitude and longitude (or X/Y coordinate used in conjunction with crs).

pollutant

Pollutant name(s).

required | scope: dynamic & static

The column name(s) of the pollutant(s) to plot. If multiple pollutants are specified and a non-pairwise statistic is supplied, the type argument will no longer be able to be used and:

Dynamic: The pollutants can be toggled between using a "layer control" menu.
Static:: The pollutants will each appear in a different panel.

Multiple pollutants prohibit the use of the type argument for non-pairwise statistics.

statistic

The statistic to be applied to each data bin in the plot

default: "prop.mean" | scope: dynamic & static

Options currently include "prop.count", "prop.mean" and "abs.count". "prop.count" sizes bins according to the proportion of the frequency of measurements. Similarly, "prop.mean" sizes bins according to their relative contribution to the mean. "abs.count" provides the absolute count of measurements in each bin.

breaks

Specifier for the number of breaks of the colour axis.

default: NULL | scope: dynamic & static

Most commonly, the number of break points. If not specified, each marker will independently break its supplied data at approximately 6 sensible break points. When breaks are specified, all markers will use the same break points. Breaks can also be used to set specific break points. For example, the argument breaks = c(0, 1, 10, 100) breaks the data into segments <1, 1-10, 10-100, >100.

latitude, longitude

The decimal latitude(Y)/longitude(X).

default: NULL | scope: dynamic & static

Column names representing the decimal latitude and longitude (or other Y/X coordinate if using a different crs). If not provided, will be automatically inferred from data by looking for a column named "lat"/"latitude" or "lon"/"lng"/"long"/"longitude" (case-insensitively).

crs

The coordinate reference system (CRS).

default: 4326 | scope: dynamic & static

The coordinate reference system (CRS) of the data, passed to sf::st_crs(). By default this is EPSG:4326, the CRS associated with the commonly used latitude and longitude coordinates. Different coordinate systems can be specified using crs (e.g., crs = 27700 for the British National Grid). Note that non-lat/lng coordinate systems will be re-projected to EPSG:4326 for plotting on the map.

type

A method to condition the data for separate plotting.

default: NULL | scope: dynamic & static

Used for splitting the input data into different groups, passed to the type argument of openair::cutData(). When type is specified:

Dynamic: The different data splits can be toggled between using a "layer control" menu.
Static:: The data splits will each appear in a different panel.

type cannot be used if multiple pollutant columns have been provided.

popup

Content for marker popups on dynamic maps.

default: NULL | scope: dynamic

Columns to be used as the HTML content for marker popups on dynamic maps. Popups may be useful to show information about the individual sites (e.g., site names, codes, types, etc.). If a vector of column names are provided they are passed to buildPopup() using its default values.

label

Content for marker hover-over on dynamic maps.

default: NULL | scope: dynamic

Column to be used as the HTML content for hover-over labels. Labels are useful for the same reasons as popups, though are typically shorter.

provider

The basemap(s) to be used.

default: "OpenStreetMap" | scope: dynamic & static

The base map(s) to be used for the map. If not provided, will default to "OpenStreetMap"/"osm" for both dynamic and static maps.

Dynamic: Any number of leaflet::providers. See http://leaflet-extras.github.io/leaflet-providers/preview/ for a list of all base maps that can be used. If multiple base maps are provided, they can be toggled between using a "layer control" interface. By default, the interface will use the provider names as labels, but users can define their own using a named vector (e.g., c("Default" = "OpenStreetMap", "Satellite" = "Esri.WorldImagery"))
Static: One of rosm::osm.types().

There is some overlap in static and dynamic providers. For example, {ggspatial} uses "osm" to specify "OpenStreetMap". When static providers are provided to dynamic maps or vice versa, {openairmaps} will attempt to substitute the correct provider string.

cols

Colours to use for plotting.

default: "turbo" | scope: dynamic & static

The colours used for plotting, passed to openair::openColours(). The default, "turbo", is a rainbow palette with relatively perceptually uniform colours.

alpha

Transparency value for polar markers.

default: 1 | scope: dynamic & static

A value between 0 (fully transparent) and 1 (fully opaque).

key

Draw individual marker legends?

default: FALSE | scope: dynamic & static

Draw a key for each individual marker? Potentially useful when limits = "free", but of limited use otherwise.

legend

Draw a shared legend?

default: TRUE | scope: dynamic & static

When all markers share the same colour scale (e.g., when limits != "free" in polarMap()), should a shared legend be created at the side of the map?

legend.position

Position of the shared legend.

default: NULL | scope: dynamic & static

When legend = TRUE, where should the legend be placed?

Dynamic: One of "topright", "topright", "bottomleft" or "bottomright". Passed to the position argument of leaflet::addLegend().
Static:: One of "top", "right", "bottom" or "left". Passed to the legend.position argument of ggplot2::theme().

legend.title

Title of the legend.

default: NULL | scope: dynamic & static

By default, when legend.title = NULL, the function will attempt to provide a sensible legend title. legend.title allows users to overwrite this - for example, to include units or other contextual information. For dynamic maps, users may wish to use HTML tags to format the title.

legend.title.autotext

Automatically format the title of the legend?

default: TRUE | scope: dynamic & static

When legend.title.autotext = TRUE, legend.title will be first run through quickTextHTML() (dynamic) or openair::quickText() (static).

control.collapsed

Show the layer control as a collapsed?

default: FALSE | scope: dynamic

For dynamic maps, should the "layer control" interface be collapsed? If TRUE, users will have to hover over an icon to view the options.

control.position

Position of the layer control menu

default: "topright" | scope: dynamic

When type != NULL, or multiple pollutants are specified, where should the "layer control" interface be placed? One of "topleft", "topright", "bottomleft" or "bottomright". Passed to the position argument of leaflet::addLayersControl().

control.autotext

Automatically format the content of the layer control menu?

default: TRUE | scope: dynamic

When control.autotext = TRUE, the content of the "layer control" interface will be first run through quickTextHTML().

d.icon

The diameter of the plot on the map in pixels.

default: 200 | scope: dynamic & static

This will affect the size of the individual polar markers. Alternatively, a vector in the form c(width, height) can be provided if a non-circular marker is desired.

d.fig

The diameter of the plots to be produced using {openair} in inches.

default: 3.5 | scope: dynamic & static

This will affect the resolution of the markers on the map. Alternatively, a vector in the form c(width, height) can be provided if a non-circular marker is desired.

static

Produce a static map?

default: FALSE

This controls whether a dynamic or static map is produced. The former is the default and is broadly more useful, but the latter may be preferable for DOCX or PDF outputs (e.g., academic papers).

static.nrow

Number of rows in a static map.

default: NULL | scope: static

Controls the number of rows of panels on a static map when multiple pollutants or type are specified; passed to the nrow argument of ggplot2::facet_wrap(). The default, NULL, results in a roughly square grid of panels.

progress

Show a progress bar?

default: TRUE | scope: dynamic & static

By default, a progress bar is shown to visualise the function's progress creating individual polar markers. This option allows this to be turned off, if desired.

...

Arguments passed on to openair::pollutionRose

key.footer: Adds additional text/labels below the scale key. See key.header for further information.
key.position: Location where the scale key is to plotted. Allowed arguments currently include “top”, “right”, “bottom” and “left”.
paddle: Either TRUE or FALSE. If TRUE plots rose using 'paddle' style spokes. If FALSE plots rose using 'wedge' style spokes.
seg: When paddle = TRUE, seg determines with width of the segments. For example, seg = 0.5 will produce segments 0.5 * angle.
normalise: If TRUE each wind direction segment is normalised to equal one. This is useful for showing how the concentrations (or other parameters) contribute to each wind sector when the proportion of time the wind is from that direction is low. A line showing the probability that the wind directions is from a particular wind sector is also shown.

control

Deprecated. Please use type.

Value

Either:

Dynamic: A leaflet object
Static: A ggplot2 object using ggplot2::coord_sf() coordinates with a ggspatial basemap

Parallel processing with mirai

Creating a directional analysis map can take a lot of time; each polar marker needs to be plot individually, and many of these require some expensive computations. openairmaps supports parallel processing with {mirai} to speed these computations up. Users may create workers by running mirai::daemons() in their R session.

mirai::daemons(4)
polarMap(polar_data, "no2")

Typically, spawning one fewer daemons than your number of available cores is a useful rule of thumb. Parallel processing will be most useful for the most computationally intensive plotting functions - i.e., polarMap() and annulusMap().

Customisation of static maps using ggplot2

As all static plots functions are ggplot2 figures, further customisation is possible using functions such as ggplot2::theme(), ggplot2::guides() and ggplot2::labs().

Subscripting pollutants (e.g., the "x" in "NOx") is achieved using the ggtext package. Therefore if you choose to override the plot theme, it is recommended to use [ggplot2::theme()] and [ggtext::element_markdown()] to define the strip.text parameter.

Legends can be removed using ggplot2::theme(legend.position = "none"), or further customised using ggplot2::guides() and either color = ggplot2::guide_colourbar() for continuous legends or color = ggplot2::guide_legend() for discrete legends.

The extent of a map can be adjusted using the xlim and ylim arguments of ggplot2::coord_sf().

polarMap(polar_data, "no2", static = TRUE) +
    ggplot2::coord_sf(
        xlim = c(-0.3, 0.2),
        ylim = c(51.2, 51.8)
    )

Examples

if (FALSE) { # \dontrun{
pollroseMap(polar_data,
  pollutant = "nox",
  statistic = "prop.count",
  provider = "CartoDB.Voyager"
)
} # }

Usage

Arguments

Value

Parallel processing with mirai

Customisation of static maps using ggplot2

See also

Examples