airbaseSplice: Function to simplify and combine airbase data imports

Description

Function to simplify and combine airbase data imports

Usage

airbaseSplice(dat, drop = TRUE)

Arguments

dat

Data (a data frame) that has been imported using the importAirbase function.

drop

Should the original columns be dropped or kept. The default is to remove (drop) them.

Value

A simplified data frame.

Details

Airbase keeps a detailed account of the instruments used for measuring different species. For the same species several different instruments can be used over time. For example, for NOx a broken instrument could be replaced by a new one. In airbase these two instruments will results in two separate time series identified through the airbase measurement_european_group_code (with numbers like 100, 101, 102). When data are imported using the importAirbase function the different measurement codes are retained in the pollutant names if more than one code is used, resulting in names like NOX|101, NOX|102 and so on.

For simple species such as NOx there is generally no reason to keep two separate time series and it would seem reasonable to combine them into a single species NOX. This is what the airbaseSplice function does. It will combine multiple measurements of the same species into a new single species. In cases where there is overlap, more recent instrument measurements take precedence over older instrument measurements.

In other cases it can be sensible to keep the different measurements of the same species separate. An example of such a case is for PM10 where, for example, moving from TEOM to FDMS measurements produces time series that cannot (or should not) be easily be merged.

Rather than combine all pollutant measurements of the same species by default it was thought important to retain this information to allow users more flexibility.

If drop = TRUE then the original columns are not retained. For example, given original columns NOX|101, NOX|102 the new data frame will have only one column NOX. Conversely, if drop = FALSE then the final data frame will have three species: NOX|101, NOX|102 and a new combined field NOX.