openair (version 1.0)

percentileRose: Function to plot percentiles by wind direction

Description

percentileRose plots percentiles by wind direction with flexible conditioning. The plot can display mutiple percentile lines or filled areas.

Usage

percentileRose(mydata, pollutant = "nox", wd = "wd", type = "default",
  percentile = c(25, 50, 75, 90, 95), smooth = FALSE, method = "default",
  cols = "default", mean = TRUE, mean.lty = 1, mean.lwd = 3,
  mean.col = "grey", fill = TRUE, intervals = NULL, angle.scale = 45,
  auto.text = TRUE, key.header = NULL, key.footer = "percentile",
  key.position = "bottom", key = TRUE, ...)

Arguments

mydata

A data frame minimally containing wd and a numeric field to plot --- pollutant.

pollutant

Mandatory. A pollutant name corresponding to a variable in a data frame should be supplied e.g. pollutant = "nox". More than one pollutant can be supplied e.g. pollutant = c("no2", "o3") provided there is only one type

wd

Name of the wind direction field.

type

type determines how the data are split i.e. conditioned, and then plotted. The default is will produce a single plot using the entire data. Type can be one of the built-in types as detailed in cutData e.g. season

percentile

The percentile value(s) to plot. Must be between 0--100. If percentile = NA then only a mean line will be shown.

smooth

Should the wind direction data be smoothed using a cyclic spline?

method

When method = "default" the supplied percentiles by wind direction are calculated. When method = "cpf" the conditional probability function (CPF) is plotted and a single (usually high) percentile level is supplied. The CPF is def

cols

Colours to be used for plotting. Options include default, increment, heat, jet and RColorBrewer colours --- see the openair openColours function for

mean

Show the mean by wind direction as a line?

mean.lty

Line type for mean line.

mean.lwd

Line width for mean line.

mean.col

Line colour for mean line.

fill

Should the percentile intervals be filled (default) or should lines be drawn (fill = FALSE).

intervals

User-supplied intervals for the scale e.g. intervals = c(0, 10, 30, 50)

angle.scale

The pollutant scale is by default shown at a 45 degree angle. Sometimes the placement of the scale may interfere with an interesting feature. The user can therefore set angle.scale to another value (between 0 and 360 degrees) to mitigate such

auto.text

Either 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.

key.header

Adds additional text/labels to the scale key. For example, passing options key.header = "header", key.footer = "footer" adds addition text above and below the scale key. These arguments are passed to drawOpenKey via quickTe

key.footer

key.header.

key.position

Location where the scale key is to plotted. Allowed arguments currently include "top", "right", "bottom" and "left".

key

Fine control of the scale key via drawOpenKey. See drawOpenKey for further details.

...

Other graphical parameters are passed onto cutData and lattice:xyplot. For example, percentileRose passes the option hemisphere = "southern" on to cutData to provide southern (rather than de

Value

• As well as generating the plot itself, percentileRose also returns an object of class openair. The object includes three main components: call, the command used to generate the plot; data, the data frame of summarised information used to make the plot; and plot, the plot itself. If retained, e.g. using output <- percentileRose(mydata, "nox"), this output can be used to recover the data, reproduce or rework the original plot or undertake further analysis.

  An openair output can be manipulated using a number of generic operations, including print, plot and summary.

Details

percentileRose calculates percentile levels of a pollutant and plots them by wind direction. One or more percentile levels can be calculated and these are displayed as either filled areas or as lines.

The wind directions are rounded to the nearest 10 degrees, consistent with surface data from the UK Met Office before a smooth is fitted. The levels by wind direction are optionally calculated using a cyclic smooth cubic spline using the option smooth. If smooth = FALSE then the data are shown in 10 degree sectors.

The percentileRose function compliments other similar functions including windRose, pollutionRose, polarFreq or polarPlot. It is most useful for showing the distribution of concentrations by wind direction and often can reveal different sources e.g. those that only affect high percentile concentrations such as a chimney stack.

Similar to other functions, flexible conditioning is available through the type option. It is easy for example to consider multiple percentile values for a pollutant by season, year and so on. See examples below.

percentileRose also offers great flexibility with the scale used and the user has fine control over both the range, interval and colour.

References

Ashbaugh, L.L., Malm, W.C., Sadeh, W.Z., 1985. A residence time probability analysis of sulfur concentrations at ground canyon national park. Atmospheric Environment 19 (8), 1263-1270.

See Also

See Also as windRose, pollutionRose, polarFreq, polarPlot

Examples

# basic percentile plot
percentileRose(mydata, pollutant = "o3")

# 50/95th percentiles of ozone, with different colours
percentileRose(mydata, pollutant = "o3", percentile = c(50, 95), col = "brewer1")

# percentiles of ozone by year, with different colours
percentileRose(mydata, type = "year", pollutant = "o3", col = "brewer1")

# percentile concentrations by season and day/nighttime..
percentileRose(mydata, type = c("season", "daylight"), pollutant = "o3", col = "brewer1")