The freqMap() function creates a map using polar frequency plots 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.
freqMap(
data,
pollutant = NULL,
statistic = "mean",
breaks = "free",
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,
...,
control = NULL
)Either:
Dynamic: A leaflet object
Static: A ggplot2 object using ggplot2::coord_sf() coordinates with a ggspatial basemap
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 name(s).
required | scope: dynamic & static
The column name(s) of the pollutant(s) to plot. If multiple pollutants are
specified 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.
The statistic that should be applied to each wind speed/direction bin.
default: "mean" | scope: dynamic & static
Can be "frequency", "mean", "median", "max" (maximum), "stdev" (standard
deviation) or "weighted.mean". The option "frequency" is the simplest and
plots the frequency of wind speed/direction in different bins. The scale
therefore shows the counts in each bin. The option "mean" (the default) will
plot the mean concentration of a pollutant (see next point) in wind
speed/direction bins, and so on. Finally, "weighted.mean" will plot the
concentration of a pollutant weighted by wind speed/direction. Each segment
therefore provides the percentage overall contribution to the total
concentration. Note that for options other than "frequency", it is necessary
to also provide the name of a pollutant. See function openair::cutData()
for further details.
Specifier for the breaks of the plot colour scale.
default: "free" | scope: dynamic & static
One of:
"fixed" which ensures all of the markers use the same colour scale.
"free" (the default) which allows all of the markers to use different
colour scales.
A numeric vector defining a sequence of numbers to use as the breaks. The
sequence could represent one with equal spacing, e.g., breaks = seq(0, 100, 10) - a scale from 0-10 in intervals of 10, or a more flexible
sequence, e.g., breaks = c(0, 1, 5, 7, 10), which may be useful for some
situations.
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).
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.
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.
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.
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.
The basemap(s) to be used.
default: "OpenStreetMap" | scope: dynamic & static
The base map(s) to be used beneath the polar markers. 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.
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. Read more about this palette at
https://research.google/blog/turbo-an-improved-rainbow-colormap-for-visualization/.
Transparency value for polar markers.
default: 1 | scope: dynamic & static
A value between 0 (fully transparent) and 1 (fully opaque).
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.
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?
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().
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.
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).
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.
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().
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().
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.
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.
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).
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.
Arguments passed on to openair::polarFreq
ws.intWind speed interval assumed. In some cases e.g. a low met mast, an interval of 0.5 may be more appropriate.
wd.nintNumber of intervals of wind direction.
grid.lineRadial spacing of grid lines.
transShould a transformation be applied? Sometimes when producing
plots of this kind they can be dominated by a few high points. The default
therefore is TRUE and a square-root transform is applied. This
results in a non-linear scale and (usually) a better representation of the
distribution. If set to FALSE a linear scale is used.
min.binThe minimum number of points allowed in a wind speed/wind
direction bin. The default is 1. A value of two requires at least 2 valid
records in each bin an so on; bins with less than 2 valid records are set
to NA. Care should be taken when using a value > 1 because of the risk of
removing real data points. It is recommended to consider your data with
care. Also, the polarFreq function can be of use in such
circumstances.
ws.upperA user-defined upper wind speed to use. This is useful for
ensuring a consistent scale between different plots. For example, to
always ensure that wind speeds are displayed between 1-10, set
ws.int = 10.
offsetoffset controls the size of the ‘hole’ in the
middle and is expressed as a percentage of the maximum wind speed. Setting
a higher offset e.g. 50 is useful for statistic =
"weighted.mean" when ws.int is greater than the maximum wind
speed. See example below.
border.colThe colour of the boundary of each wind speed/direction bin. The default is transparent. Another useful choice sometimes is "white".
key.headerAdds additional text/labels to the scale key. For example,
passing the options key.header = "header", key.footer = "footer1"
adds addition text above and below the scale key. These arguments are
passed to drawOpenKey via quickText, applying the
auto.text argument, to handle formatting.
key.footersee key.footer.
key.positionLocation where the scale key is to plotted. Allowed
arguments currently include "top", "right", "bottom"
and "left".
auto.textEither TRUE (default) or FALSE. If TRUE
titles and axis labels will automatically try and format pollutant names
and units properly e.g. by subscripting the `2' in NO2.
Deprecated. Please use type.
As the outputs of the static directional analysis functions are ggplot2
figures, further customisation is possible using functions such as
ggplot2::theme(), ggplot2::guides() and ggplot2::labs().
If multiple pollutants are specified, subscripting (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.
When arguments like limits, percentile or breaks are defined, a
legend is automatically added to the figure. 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 fill = ggplot2::guide_legend() for discrete
legends.
openair::polarFreq()
Other directional analysis maps:
annulusMap(),
diffMap(),
percentileMap(),
polarMap(),
pollroseMap(),
windroseMap()
if (FALSE) {
freqMap(polar_data,
pollutant = "nox",
statistic = "mean",
provider = "CartoDB.Voyager"
)
}
Run the code above in your browser using DataLab