Calculate rolling quantile pollutant values — rollingQuantile • openair

This is a utility function mostly designed to calculate rolling quantile statistics. The function will try and fill in missing time gaps to get a full time sequence but return a data frame with the same number of rows supplied.

Usage

rollingQuantile(
  mydata,
  pollutant = "o3",
  width = 8L,
  type = "default",
  data.thresh = 75,
  align = c("centre", "center", "left", "right"),
  probs = 0.5,
  date.pad = FALSE,
  ...
)

Arguments

mydata: A data frame containing a date field. mydata must contain a date field in Date or POSIXct format. The input time series must be regular, e.g., hourly, daily.
pollutant: The name of a pollutant, e.g., pollutant = "o3".
width: The averaging period (rolling window width) to use, e.g., width = 8 will generate 8-hour rolling mean values when hourly data are analysed.
type: Used for splitting the data further. Passed to cutData().
data.thresh: The % data capture threshold. No values are calculated if data capture over the period of interest is less than this value. For example, with width = 8 and data.thresh = 75 at least 6 hours are required to calculate the mean, else NA is returned.
align: Specifies how the moving window should be aligned. "right" means that the previous hours (including the current) are averaged. "left" means that the forward hours are averaged. "centre" (or "center" - the default) centres the current hour in the window.
probs: Probability for quantile calculate. A number between 0 and 1. Can be more than length one e.g. probs = c(0.05, 0.95).
date.pad: Should missing dates be padded? Default is FALSE.
...: Additional parameters passed to cutData(). For use with type.

Value

A tibble with new columns for the rolling quantile value and the number of valid values used.

Author

David Carslaw

Examples

# rolling 24-hour 0.05 and 0.95 quantile for ozone
mydata <- rollingQuantile(mydata,
  pollutant = "o3", width = 24, data.thresh = 75, align = "right", probs = c(0.05, 0.95)
)