get dimensions from stars object

st_dimensions(.x, ...)

# S3 method for stars
st_dimensions(.x, ...)

# 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, ..., max = FALSE, center = NA)

Arguments

.x

object to retrieve dimensions information from

...

further arguments

.raster

length 2 character array with names (if any) of the raster dimensions

affine

numeric; specify parameters of the affine transformation

cell_midpoints

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

point

logical; does the pixel value (measure) refer to a point (location) value or to an pixel (area) summary value?

which

integer or character; index or name of the dimension to be changed

values

values for this dimension (e.g. sfc list-column)

names

character; new names vector for (all) dimensions, ignoring which

xy

length-2 character vector; (new) names for the x and y raster dimensions

max

logical; if TRUE return the end, rather than the beginning of an interval

center

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

Value

the dimensions attribute of x, of class dimensions

Details

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.

Examples

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): #> L7_ETMs.tif #> Min. : 1.00 #> 1st Qu.: 54.00 #> Median : 69.00 #> Mean : 68.91 #> 3rd Qu.: 86.00 #> Max. :255.00 #> dimension(s): #> from to offset delta refsys point values #> x 1 349 288776 28.5 +proj=utm +zone=25 +south... FALSE NULL #> y 1 352 9120761 -28.5 +proj=utm +zone=25 +south... FALSE NULL #> band_number 1 6 NA NA NA TRUE 1,...,7 #> #> x [x] #> y [y] #> band_number
# 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): #> L7_ETMs.tif #> Min. : 1.00 #> 1st Qu.: 54.00 #> Median : 69.00 #> Mean : 68.91 #> 3rd Qu.: 86.00 #> Max. :255.00 #> dimension(s): #> from to offset delta refsys point #> x 1 349 288776 28.5 +proj=utm +zone=25 +south... FALSE #> y 1 352 9120761 -28.5 +proj=utm +zone=25 +south... FALSE #> bandwidth_midpoint 1 6 NA NA udunits TRUE #> values #> 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): #> L7_ETMs.tif #> Min. : 1.00 #> 1st Qu.: 54.00 #> Median : 69.00 #> Mean : 68.91 #> 3rd Qu.: 86.00 #> Max. :255.00 #> dimension(s): #> from to offset delta refsys point #> x 1 349 288776 28.5 +proj=utm +zone=25 +south... FALSE #> y 1 352 9120761 -28.5 +proj=utm +zone=25 +south... FALSE #> bandwidth 1 6 NA NA udunits NA #> values #> x NULL [x] #> y NULL [y] #> bandwidth [0.45,0.515) [um],...,[2.08,2.35) [um]