openair (version 3.0.0)

rollingQuantile: Calculate rolling quantile pollutant values

Description

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,
  ...
)

Value

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

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.

...

Passed to cutData() for use with type.

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)
)