Polar annulus plots on interactive leaflet mapsSource:
annulusMap() creates a
leaflet map using polar annulus plots as markers.
Any number of pollutants can be specified using the
pollutant argument, and
multiple layers of markers can be added and toggled between using
annulusMap( data, pollutant = NULL, period = "hour", limits = "free", latitude = NULL, longitude = NULL, control = NULL, popup = NULL, label = NULL, provider = "OpenStreetMap", cols = "turbo", alpha = 1, key = FALSE, draw.legend = TRUE, collapse.control = FALSE, d.icon = 200, d.fig = 3.5, type = deprecated(), ... )
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,
datamust include a decimal latitude and longitude.
The column name(s) of the pollutant(s) to plot. If multiple pollutants are specified, they can be toggled between using a "layer control" interface.
This determines the temporal period to consider. Options are "hour" (the default, to plot diurnal variations), "season" to plot variation throughout the year, "weekday" to plot day of the week variation and "trend" to plot the trend by wind direction.
"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 in the form
c(lower, upper)used to define the colour scale. For example,
limits = c(0, 100)would force the plot limits to span 0-100.
- latitude, longitude
The decimal latitude/longitude. If not provided, will be automatically inferred from data by looking for a column named "lat"/"latitude" or "lon"/"lng"/"long"/"longitude" (case-insensitively).
Used for splitting the input data into different groups which can be selected between using a "layer control" interface, passed to the
controlcannot be used if multiple
pollutantcolumns have been provided.
Columns to be used as the HTML content for marker popups. 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.
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 base map(s) to be used. 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"))
The colours used for plotting. See
openair::openColours()for more information.
The alpha transparency to use for the plotting surface (a value between 0 and 1 with zero being fully transparent and 1 fully opaque).
Should a key for each marker be drawn? Default is
limitsare specified, should a shared legend be created at the side of the map? Default is
Should the "layer control" interface be collapsed? Defaults to
The diameter of the plot on the map in pixels. 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
openairin inches. 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.
Arguments passed on to
Two plot resolutions can be set: “normal” and “fine” (the default).
Should the results be calculated in local time that includes a treatment of daylight savings time (DST)? The default is not to consider DST issues, provided the data were imported without a DST offset. Emissions activity tends to occur at local time e.g. rush hour is at 8 am every day. When the clocks go forward in spring, the emissions are effectively released into the atmosphere typically 1 hour earlier during the summertime i.e. when DST applies. When plotting diurnal profiles, this has the effect of “smearing-out” the concentrations. Sometimes, a useful approach is to express time as local time. This correction tends to produce better-defined diurnal profiles of concentration (or other variables) and allows a better comparison to be made with emissions/activity data. If set to
FALSEthen GMT is used. Examples of usage include
local.tz = "Europe/London",
local.tz = "America/New_York". See
importfor more details.
The statistic that should be applied to each wind speed/direction bin. Can be “mean” (default), “median”, “max” (maximum), “frequency”. “stdev” (standard deviation), “weighted.mean” or “cpf” (Conditional Probability Function). Because of the smoothing involved, the colour scale for some of these statistics is only to provide an indication of overall pattern and should not be interpreted in concentration units e.g. for
statistic = "weighted.mean"where the bin mean is multiplied by the bin frequency and divided by the total frequency. In many cases using
polarFreqwill be better. Setting
statistic = "weighted.mean"can be useful because it provides an indication of the concentration * frequency of occurrence and will highlight the wind speed/direction conditions that dominate the overall mean.
statistic = "percentile"or
statistic = "cpf"then
percentileis used, expressed from 0 to 100. Note that the percentile value is calculated in the wind speed, wind direction ‘bins’. For this reason it can also be useful to set
min.binto ensure there are a sufficient number of points available to estimate a percentile. See
quantilefor more details of how percentiles are calculated.
The width of the annulus; can be “normal” (the default), “thin” or “fat”.
The 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
polarFreqfunction can be of use in such circumstances.
Setting this option to
TRUE(the default) removes points from the plot that are too far from the original data. The smoothing routines will produce predictions at points where no data exist i.e. they predict. By removing the points too far from the original data produces a plot where it is clear where the original data lie. If set to
FALSEmissing data will be interpolated.
type = "trend"(default),
date.pad = TRUEwill pad-out missing data to the beginning of the first year and the end of the last year. The purpose is to ensure that the trend plot begins and ends at the beginning or end of year.
The default is
TRUE. Sometimes if smoothing data with steep gradients it is possible for predicted values to be negative.
force.positive = TRUEensures that predictions remain positive. This is useful for several reasons. First, with lots of missing data more interpolation is needed and this can result in artefacts because the predictions are too far from the original data. Second, if it is known beforehand that the data are all positive, then this option carries that assumption through to the prediction. The only likely time where setting
force.positive = FALSEwould be if background concentrations were first subtracted resulting in data that is legitimately negative. For the vast majority of situations it is expected that the user will not need to alter the default option.
The smoothing value supplied to
gamfor the temporal and wind direction components, respectively. In some cases e.g. a trend plot with less than 1-year of data the smoothing with the default values may become too noisy and affected more by outliers. Choosing a lower value of
k(say 10) may help produce a better plot.
TRUEconcentrations are normalised by dividing by their mean value. This is done after fitting the smooth surface. This option is particularly useful if one is interested in the patterns of concentrations for several pollutants on different scales e.g. NOx and CO. Often useful if more than one
Adds 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
quickText, applying the
auto.textargument, to handle formatting.
Location where the scale key is to plotted. Allowed arguments currently include
TRUEtitles and axis labels will automatically try and format pollutant names and units properly e.g. by subscripting the `2' in NO2.