subset stars objects

Source: R/subset.R

subset stars objects

# S3 method for stars
[(x, i = TRUE, ..., drop = FALSE, crop = !is_curvilinear(x))

# S3 method for stars
[(x, i) <- value

st_flip(x, which = 1)

Arguments

x

object of class stars
i

first selector: integer, logical or character vector indicating attributes to select, or object of class sf or sfc used as spatial selector; see details
...

further (logical or integer vector) selectors, matched by order, to select on individual dimensions
drop

logical; if TRUE, degenerate dimensions (with only one value) are dropped
crop

logical; if TRUE and parameter i is a spatial geometry (sf or sfc) object, the extent (bounding box) of the result is cropped to match the extent of i using st_crop. Cropping curvilinear grids is not supported.
value

array of dimensions equal to those in x, or a vector or value that will be recycled to such an array
which

character or integer; dimension(s) to be flipped

Value

st_flip flips (reverts) the array values along the chosen dimension without(s) changing the dimension properties

Details

if i is an object of class sf, sfc or bbox, the spatial subset covering this geometry is selected, possibly followed by cropping the extent. Array values for which the cell centre is not inside the geometry are assigned NA.

in an assignment (or replacement form, [<-), argument i needs to be a stars object with dimensions identical to x, and value will be recycled to the dimensions of the arrays in x.

Examples

tif = system.file("tif/L7_ETMs.tif", package = "stars")
x = read_stars(tif)
x[,,,1:3] # select bands

#> stars object with 3 dimensions and 1 attribute
#> attribute(s):
#>              Min. 1st Qu. Median     Mean 3rd Qu. Max.
#> L7_ETMs.tif    21      58     70 70.36041      83  255
#> dimension(s):
#>      from  to  offset delta                       refsys point values x/y
#> x       1 349  288776  28.5 UTM Zone 25, Southern Hem... FALSE   NULL [x]
#> y       1 352 9120761 -28.5 UTM Zone 25, Southern Hem... FALSE   NULL [y]
#> band    1   3      NA    NA                           NA    NA   NULL    
x[,1:100,100:200,] # select x and y by range

#> stars object with 3 dimensions and 1 attribute
#> attribute(s):
#>              Min. 1st Qu. Median     Mean 3rd Qu. Max.
#> L7_ETMs.tif    13      54     65 67.21531      77  252
#> dimension(s):
#>      from  to  offset delta                       refsys point values x/y
#> x       1 100  288776  28.5 UTM Zone 25, Southern Hem... FALSE   NULL [x]
#> y     100 200 9120761 -28.5 UTM Zone 25, Southern Hem... FALSE   NULL [y]
#> band    1   6      NA    NA                           NA    NA   NULL    
x["L7_ETMs.tif"] # select attribute

#> stars object with 3 dimensions and 1 attribute
#> attribute(s):
#>              Min. 1st Qu. Median     Mean 3rd Qu. Max.
#> L7_ETMs.tif     1      54     69 68.91242      86  255
#> dimension(s):
#>      from  to  offset delta                       refsys point values x/y
#> x       1 349  288776  28.5 UTM Zone 25, Southern Hem... FALSE   NULL [x]
#> y       1 352 9120761 -28.5 UTM Zone 25, Southern Hem... FALSE   NULL [y]
#> band    1   6      NA    NA                           NA    NA   NULL    
xy = structure(list(x = c(293253.999046018, 296400.196497684), y = c(9113801.64775462,
9111328.49619133)), .Names = c("x", "y"))
pts = st_as_sf(data.frame(do.call(cbind, xy)), coords = c("x", "y"), crs = st_crs(x))
image(x, axes = TRUE)

plot(st_as_sfc(st_bbox(pts)), col = NA, add = TRUE)

bb = st_bbox(pts)
(xx = x[bb])

#> stars object with 3 dimensions and 1 attribute
#> attribute(s):
#>              Min. 1st Qu. Median     Mean 3rd Qu. Max.
#> L7_ETMs.tif     3      56     73 70.87303      89  255
#> dimension(s):
#>      from  to  offset delta                       refsys point values x/y
#> x     158 268  288776  28.5 UTM Zone 25, Southern Hem... FALSE   NULL [x]
#> y     245 331 9120761 -28.5 UTM Zone 25, Southern Hem... FALSE   NULL [y]
#> band    1   6      NA    NA                           NA    NA   NULL    
image(xx)

plot(st_as_sfc(bb), add = TRUE, col = NA)

image(x)

pt = st_point(c(x = 290462.103109179, y = 9114202.32594085))
buf = st_buffer(st_sfc(pt, crs = st_crs(x)), 1500)
plot(buf, add = TRUE)


buf = st_sfc(st_polygon(list(st_buffer(pt, 1500)[[1]], st_buffer(pt, 1000)[[1]])),
   crs = st_crs(x))
image(x[buf])

plot(buf, add = TRUE, col = NA)

image(x[buf, crop=FALSE])

plot(buf, add = TRUE, col = NA)

lc = read_stars(system.file("tif/lc.tif", package = "stars"))
x = c(orig = lc, 
      flip_x = st_flip(lc, "x"), 
      flip_y = st_flip(lc, "y"), 
      flip_xy = st_flip(lc, c("x", "y")), 
      along = 3)
plot(x)

#> downsample set to c(0,0,1)