get dimensions from stars object
st_dimensions(.x, ...)
# S3 method for stars
st_dimensions(.x, ...)
st_dimensions(x) <- value
# S3 method for stars
st_dimensions(x) <- value
# S3 method for stars_proxy
st_dimensions(x) <- value
# S3 method for list
st_dimensions(x) <- value
# S3 method for array
st_dimensions(.x, ...)
# S3 method for default
st_dimensions(
.x,
...,
.raster,
affine = c(0, 0),
cell_midpoints = FALSE,
point = FALSE
)
st_set_dimensions(
.x,
which,
values = NULL,
point = NULL,
names = NULL,
xy,
...
)
st_get_dimension_values(.x, which, ..., where = NA, max = FALSE, center = NA)object to retrieve dimensions information from
further arguments
object of class dimensions
new object of class dimensions, with matching dimensions
length 2 character array with names (if any) of the raster dimensions
numeric; specify parameters of the affine transformation
logical; if TRUE AND the dimension values are strictly regular, the values are interpreted as the cell midpoint values rather than the cell offset values when calculating offset (i.e., the half-cell-size correction is applied); can have a value for each dimension, or else is recycled
logical; does the pixel value (measure) refer to a point (location) value or to an pixel (area) summary value?
integer or character; index or name of the dimension to be changed
values for this dimension (e.g. sfc list-column), or length-1 dimensions object
character; vector with new names for all dimensions, or with the single new name for the dimension indicated by which
length-2 character vector; (new) names for the x and y raster dimensions
character, one of 'start', 'center' or 'end'. Set to NA (default) to ignore and use max and center explictly. This argument provides a convenient alternative to setting max and center.
logical; if TRUE return the end, rather than the beginning of an interval
logical; if TRUE return the center of an interval; if NA return the center for raster dimensions, and the start of intervals in other cases
the dimensions attribute of x, of class dimensions
dimensions can be specified in two ways. The simplest is to pass a vector with numeric values for a numeric dimension, or character values for a categorical dimension. Parameter cell_midpoints is used to specify whether numeric values refer to the offset (start) of a dimension interval (default), or to the center; the center case is only available for regular dimensions. For rectilinear numeric dimensions, one can specify either a vector with cell borders (start values), or a data.frame with two columns named "start" and "end", with the respective interval start and end values. In the first case, the end values are computed from the start values by assuming the last two intervals have equal width.
x = read_stars(system.file("tif/L7_ETMs.tif", package = "stars"))
# Landsat 7 ETM+ band semantics: https://landsat.gsfc.nasa.gov/the-enhanced-thematic-mapper-plus/
# set bands to values 1,2,3,4,5,7:
(x1 = st_set_dimensions(x, "band", values = c(1,2,3,4,5,7), names = "band_number", point = TRUE))
#> 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 SIRGAS 2000 / UTM zone 25S FALSE NULL [x]
#> y 1 352 9120761 -28.5 SIRGAS 2000 / UTM zone 25S FALSE NULL [y]
#> band_number 1 6 NA NA NA TRUE 1,...,7
# set band values as bandwidth
rbind(c(0.45,0.515), c(0.525,0.605), c(0.63,0.69), c(0.775,0.90), c(1.55,1.75), c(2.08,2.35)) %>%
units::set_units("um") -> bw # or: units::set_units(µm) -> bw
# set bandwidth midpoint:
(x2 = st_set_dimensions(x, "band", values = 0.5 * (bw[,1]+bw[,2]),
names = "bandwidth_midpoint", point = TRUE))
#> 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
#> x 1 349 288776 28.5 SIRGAS 2000 / UTM zone 25S FALSE
#> y 1 352 9120761 -28.5 SIRGAS 2000 / UTM zone 25S FALSE
#> bandwidth_midpoint 1 6 NA NA udunits TRUE
#> values x/y
#> x NULL [x]
#> y NULL [y]
#> bandwidth_midpoint 0.4825 [um],...,2.215 [um]
# set bandwidth intervals:
(x3 = st_set_dimensions(x, "band", values = make_intervals(bw), names = "bandwidth"))
#> 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
#> x 1 349 288776 28.5 SIRGAS 2000 / UTM zone 25S FALSE
#> y 1 352 9120761 -28.5 SIRGAS 2000 / UTM zone 25S FALSE
#> bandwidth 1 6 NA NA udunits NA
#> values x/y
#> x NULL [x]
#> y NULL [y]
#> bandwidth [0.45,0.515) [um],...,[2.08,2.35) [um]
m = matrix(1:20, nrow = 5, ncol = 4)
dim(m) = c(x = 5, y = 4) # named dim
(s = st_as_stars(m))
#> stars object with 2 dimensions and 1 attribute
#> attribute(s):
#> Min. 1st Qu. Median Mean 3rd Qu. Max.
#> A1 1 5.75 10.5 10.5 15.25 20
#> dimension(s):
#> from to offset delta point x/y
#> x 1 5 0 1 FALSE [x]
#> y 1 4 0 1 FALSE [y]
st_get_dimension_values(s, 'x', where = "start")
#> [1] 0 1 2 3 4
st_get_dimension_values(s, 'x', center = FALSE)
#> [1] 0 1 2 3 4
st_get_dimension_values(s, 'x', where = "center")
#> [1] 0.5 1.5 2.5 3.5 4.5
st_get_dimension_values(s, 'x', center = TRUE)
#> [1] 0.5 1.5 2.5 3.5 4.5
st_get_dimension_values(s, 'x', where = "end")
#> [1] 1 2 3 4 5
st_get_dimension_values(s, 'x', max = TRUE)
#> [1] 1 2 3 4 5