timeProp: Time series plot with categories shown as a stacked bar chart

In openair: Tools for the Analysis of Air Pollution Data

Time series plot with categories shown as a stacked bar chart

Description

This function shows time series plots as stacked bar charts. The different categories in the bar chart are made up from a character or factor variable in a data frame. The function is primarily developed to support the plotting of cluster analysis output from polarCluster() and trajCluster() that consider local and regional (back trajectory) cluster analysis respectively. However, the function has more general use for understanding time series data.

Usage

timeProp(
  mydata,
  pollutant = "nox",
  proportion = "wd",
  avg.time = "day",
  type = "default",
  cols = "Set1",
  normalise = FALSE,
  x.relation = "same",
  y.relation = "same",
  key.columns = 1,
  key.position = "right",
  key.title = proportion,
  strip.position = "top",
  date.breaks = 7,
  date.format = NULL,
  auto.text = TRUE,
  plot = TRUE,
  key = NULL,
  ...
)

Arguments

mydata	A data frame containing the fields date, pollutant and a splitting variable proportion
pollutant	Name of the pollutant to plot contained in mydata.
proportion	The splitting variable that makes up the bars in the bar chart, defaulting to "wd". Could be "cluster" if the output from polarCluster() or trajCluster() is being analysed. If proportion is a numeric variable it is split into 4 quantiles (by default) by cutData(). If proportion is a factor or character variable then the categories are used directly.
avg.time	This defines the time period to average to. Can be "sec", "min", "hour", "day", "DSTday", "week", "month", "quarter" or "year". For much increased flexibility a number can precede these options followed by a space. For example, an average of 2 months would be avg.time = "2 month". In addition, avg.time can equal "season", in which case 3-month seasonal values are calculated with spring defined as March, April, May and so on. Note that avg.time when used in timeProp should be greater than the time gap in the original data. For example, avg.time = "day" for hourly data is OK, but avg.time = "hour" for daily data is not.
type	Character string(s) defining how data should be split/conditioned before plotting. "default" produces a single panel using the entire dataset. Any other options will split the plot into different panels - a roughly square grid of panels if one type is given, or a 2D matrix of panels if two types are given. type is always passed to cutData(), and can therefore be any of: A built-in type defined in cutData() (e.g., "season", "year", "weekday", etc.). For example, type = "season" will split the plot into four panels, one for each season. The name of a numeric column in mydata, which will be split into n.levels quantiles (defaulting to 4). The name of a character or factor column in mydata, which will be used as-is. Commonly this could be a variable like "site" to ensure data from different monitoring sites are handled and presented separately. It could equally be any arbitrary column created by the user (e.g., whether a nearby possible pollutant source is active or not). Most openair plotting functions can take two type arguments. If two are given, the first is used for the columns and the second for the rows.
cols	Colours to use for plotting. Can be a pre-set palette (e.g., "turbo", "viridis", "tol", "Dark2", etc.) or a user-defined vector of R colours (e.g., c("yellow", "green", "blue", "black") - see colours() for a full list) or hex-codes (e.g., c("#30123B", "#9CF649", "#7A0403")). See openColours() for more details.
normalise	If normalise = TRUE then each time interval is scaled to 100. This is helpful to show the relative (percentage) contribution of the proportions.
x.relation, y.relation	This determines how the x- and y-axis scales are plotted. "same" ensures all panels use the same scale and "free" will use panel-specific scales. The latter is a useful setting when plotting data with very different values.
key.columns	Number of columns to be used in a categorical legend. With many categories a single column can make to key too wide. The user can thus choose to use several columns by setting key.columns to be less than the number of categories.
key.position	Location where the legend is to be placed. Allowed arguments include "top", "right", "bottom", "left" and "none", the last of which removes the legend entirely.
key.title	Used to set the title of the legend. The legend title is passed to quickText() if auto.text = TRUE.
strip.position	Location where the facet 'strips' are located when using type. When one type is provided, can be one of "left", "right", "bottom" or "top". When two types are provided, this argument defines whether the strips are "switched" and can take either "x", "y", or "both". For example, "x" will switch the 'top' strip locations to the bottom of the plot.
date.breaks	Number of major x-axis intervals to use. The function will try and choose a sensible number of dates/times as well as formatting the date/time appropriately to the range being considered. The user can override this behaviour by adjusting the value of date.breaks up or down.
date.format	This option controls the date format on the x-axis. A sensible format is chosen by default, but the user can set date.format to override this. For format types see strptime(). For example, to format the date like "Jan-2012" set date.format = "\%b-\%Y".
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". Passed to quickText().
plot	When openair plots are created they are automatically printed to the active graphics device. plot = FALSE deactivates this behaviour. This may be useful when the plot data is of more interest, or the plot is required to appear later (e.g., later in a Quarto document, or to be saved to a file).
key	Deprecated; please use key.position. If FALSE, sets key.position to "none".
...	Addition options are passed on to cutData() for type handling. Some additional arguments are also available: xlab, ylab and main override the x-axis label, y-axis label, and plot title. layout sets the layout of facets - e.g., layout(2, 5) will have 2 columns and 5 rows. fontsize overrides the overall font size of the plot. border sets the border colour of each bar.

Details

In order to plot time series in this way, some sort of time aggregation is needed, which is controlled by the option avg.time.

The plot shows the value of pollutant on the y-axis (averaged according to avg.time). The time intervals are made up of bars split according to proportion. The bars therefore show how the total value of pollutant is made up for any time interval.

Value

an openair object

Author(s)

David Carslaw

Jack Davison

See Also

Other time series and trend functions: TheilSen(), calendarPlot(), smoothTrend(), timePlot(), timeVariation()

Other cluster analysis functions: polarCluster(), trajCluster()

Examples

# monthly plot of SO2 showing the contribution by wind sector
timeProp(mydata, pollutant = "so2", avg.time = "month", proportion = "wd")

openair documentation built on April 2, 2026, 9:07 a.m.