over-methods: consistent spatio-temporal overlay for objects inheriting from ST

Description

consistent spatio-temporal overlay for STF, STS and STI objects, as well as their *DF counterpart: retrieves the indexes or attributes from one geometry at the spatio-temporal points of another

Usage

# S4 method for STF,STF
over(x, y, returnList = FALSE, fn = NULL, ...)
# S4 method for xts,xts
over(x, y, returnList = FALSE, fn = NULL, ...)
# S4 method for ST
aggregate(x, by, FUN, …, simplify = TRUE)

Arguments

geometry (S/T locations) of the queries

layer from which the geometries or attributes are queried

returnList

logical; determines whether a list is returned, or an index vector

(optional) a function; see value

geometry over which attributes in x are aggregated (this can be a Spatial* geometry, or a ST* geometry), or temporal aggregation, such as "month", "10 minutes", or a function such as as.yearmon; see aggregate.zoo. In case x is of class STFDF, argument by may be "time" or "space", in which cases aggregation over all time or all space is carried out.

FUN

aggregation function

simplify

boolean; if TRUE, and space or time dimensions can be dropped, the simpler (Spatial or xts) object will be returned

...

arguments passed on to function fn or FUN

Value

an object of length length(x), or a data.frame with number of rows equal to length(x). If returnList is FALSE, a vector with indices of y for each geometry (point, grid cell centre, polygon or lines x time point) in x. if returnList is TRUE, a list of length length(x), with list element i the vector of indices of the geometries in y that correspond to the $i$-th geometry in x.

The aggregate method for ST objects aggregates the attribute values of x over the geometry (space, time, or space-time) of by, using aggregation function FUN.

For the matching of time intervals, see timeMatch.

For setting, or retrieving whether time represents intervals, see timeIsInterval.

Methods

x = "STF", y = "STF"
x = "xts", y = "xts": finds the row index of the instance or interval of time instances of x matching to y. Only if timeIsInterval(x) == TRUE, intervals are sought. In that case, time intervals start at the time instance of a record, and end at the next. The last time interval length is set to the interval length of the one-but-last (non-zero) interval. In case of a single time instance for y, its interval is right-open.

References

http://www.jstatsoft.org/v51/i07/