query function

Query a SpatVectorProxy object

Query a SpatVectorProxy to extract a subset methods

## 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)

See Also

vect

Returns

SpatVector

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