spacetime: over – R documentation

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over

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

Arguments

`x`	geometry (S/T locations) of the queries
`y`	layer from which the geometries or attributes are queried
`returnList`	logical; determines whether a list is returned, or an index vector
`fn`	(optional) a function; see value
`by`	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.

Note

See also over; methods intersecting SpatialLines with anything else, or SpatialPolygons with SpatialPolygons, need rgeos to be loaded first.

Author(s)

Edzer Pebesma, edzer.pebesma@uni-muenster.de

References

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