query: Query a SpatVectorProxy object

In terra: Spatial Data Analysis

Query a SpatVectorProxy object

Description

Query a SpatVectorProxy to extract a subset

Usage

## S4 method for signature 'SpatVectorProxy'
query(x, start=1, n=nrow(x), vars=NULL, where=NULL, 
    extent=NULL, filter=NULL, sql=NULL, what="")

Arguments

x	SpatVectorProxy
start	positive integer. The record to start reading at
n	positive integer. The number of records requested
vars	character. Variable names. Must be a subset of names(x)
where	character. expression like "NAME_1='California' AND ID > 3" , to subset records. Note that start and n are applied after executing the where statement
extent	Spat* object. The extent of the object is used as a spatial filter to select the geometries to read. Ignored if filter is not NULL
filter	SpatVector. Used as a spatial filter to select geometries to read (the convex hull is used for lines or points)
sql	character. Arbitrary SQL statement. If used, arguments "start", "n", "vars" and "where" are ignored
what	character indicating what to read. Either "" for geometries and attributes, or "geoms" to only read the geometries, "attributes" to only read the attributes (that are returned as a data.frame)

Value

SpatVector

See Also

vect

Examples

f <- system.file("ex/lux.shp", package="terra")
v <- vect(f, proxy=TRUE)
v

x <- query(v, vars=c("ID_2", "NAME_2"), start=5, n=2)
x

query(v, vars=c("ID_2", "NAME_1", "NAME_2"), where="NAME_1='Grevenmacher' AND ID_2 > 6")

## with an extent
e <- ext(5.9, 6.3, 49.9, 50) 
x <- query(v, extent=e)

## with polygons
p <- as.polygons(e)
x <- query(v, filter=p)
x

terra documentation built on Oct. 14, 2024, 5:07 p.m.