st_crop {stars}

crop a stars object

Description

crop a stars object

Usage

## S3 method for class 'stars_proxy'
st_crop(
  x,
  y,
  ...,
  crop = TRUE,
  epsilon = sqrt(.Machine$double.eps),
  collect = TRUE
)

## S3 method for class 'stars'
st_crop(
  x,
  y,
  ...,
  crop = TRUE,
  epsilon = sqrt(.Machine$double.eps),
  as_points = all(st_dimension(y) == 2, na.rm = TRUE),
  normalize = FALSE
)

Arguments

x

object of class stars

y

object of class sf, sfc or bbox; see Details below.

...

ignored

crop

logical; if TRUE, the spatial extent of the returned object is cropped to still cover obj, if FALSE, the extent remains the same but cells outside y are given NA values.

epsilon

numeric; factor to shrink the bounding box of y towards its center before cropping.

collect

logical; if TRUE, repeat cropping on stars object, i.e. after data has been read

as_points

logical; only relevant if y is of class sf or sfc: if FALSE, treat x as a set of points, else as a set of small polygons. Default: TRUE if y is two-dimensional, else FALSE; see Details

normalize

logical; if TRUE then pass the cropped object to st_normalize before returning.

Details

for raster x, st_crop selects cells that intersect with y. For intersection, are raster cells interpreted as points or as small polygons? If y is of class stars, x raster cells are interpreted as points; if y is of class bbox, x cells are interpreted as cells (small polygons). Otherwise, if as_points is not given, cells are interpreted as points if y has a two-dimensional geometry.

Examples

l7 = read_stars(system.file("tif/L7_ETMs.tif", package = "stars"))
d = st_dimensions(l7)

# area around cells 3:10 (x) and 4:11 (y):
offset = c(d[["x"]]$offset, d[["y"]]$offset)
res = c(d[["x"]]$delta, d[["y"]]$delta)
bb = st_bbox(c(xmin = offset[1] + 2 * res[1],
	ymin = offset[2] + 11 * res[2],
	xmax = offset[1] + 10 * res[1],
	ymax = offset[2] +  3 * res[2]), crs = st_crs(l7))
l7[bb]
# equivalent:
st_crop(l7, bb)

plot(l7[,1:13,1:13,1], reset = FALSE)
image(l7[bb,,,1], add = TRUE, col = sf.colors())
plot(st_as_sfc(bb), add = TRUE, border = 'green', lwd = 2)

# slightly smaller bbox:
bb = st_bbox(c(xmin = offset[1] + 2.1 * res[1],
	ymin = offset[2] + 10.9 * res[2],
	xmax = offset[1] +  9.9 * res[1],
	ymax = offset[2] +  3.1 * res[2]), crs = st_crs(l7))
l7[bb]

plot(l7[,1:13,1:13,1], reset = FALSE)
image(l7[bb,,,1], add = TRUE, col = sf.colors())
plot(st_as_sfc(bb), add = TRUE, border = 'green', lwd = 2)

# slightly larger bbox:
bb = st_bbox(c(xmin = offset[1] + 1.9 * res[1],
	ymin = offset[2] + 11.1 * res[2],
	xmax = offset[1] + 10.1 * res[1],
	ymax = offset[2] +  2.9 * res[2]), crs = st_crs(l7))
l7[bb]

plot(l7[,1:13,1:13,1], reset = FALSE)
image(l7[bb,,,1], add = TRUE, col = sf.colors())
plot(st_as_sfc(bb), add = TRUE, border = 'green', lwd = 2)

# half a cell size larger bbox:
bb = st_bbox(c(xmin = offset[1] + 1.49 * res[1],
	ymin = offset[2] + 11.51 * res[2],
	xmax = offset[1] + 10.51 * res[1],
	ymax = offset[2] +  2.49 * res[2]), crs = st_crs(l7))
l7[bb]

plot(l7[,1:13,1:13,1], reset = FALSE)
image(l7[bb,,,1], add = TRUE, col = sf.colors())
plot(st_as_sfc(bb), add = TRUE, border = 'green', lwd = 2)