The openair project » Examples of usage » Trend Analysis
Trend analysis is a key component of many analyses of air pollution data. openair has several ways of undertaking trend analysis.
There are two main functions: smoothTrend and MannKendall, which serve different
purposes – the latter useful for quantification.
Both these functions are highly flexible and there are many examples of usage in the manual.
In the example below, we use several options in the function smoothTrend to plot ozone trends.
First, we choose to deseasonalise the data, then we choose to plot percentiles (the 5th, 50th, 75th and 95th),
then we set type to 'wd'. The latter option recognises it
is meant to plot by wind sector and the layout of the plot is adjusted automatically.
SmoothTrend(mydata, pollutant = "o3", deseason = TRUE,
statistic = "percentile", percentile = c(25, 50, 75, 95),
type = "wd")