reduce_space.cube: Reduce a data cube over spatial (x,y or lat,lon) dimensions

In gdalcubes: Earth Observation Data Cubes from Satellite Image Collections

Reduce a data cube over spatial (x,y or lat,lon) dimensions

Description

Create a proxy data cube, which applies one or more reducer functions to selected bands over spatial slices of a data cube

Usage

## S3 method for class 'cube'
reduce_space(x, expr, ..., FUN, names = NULL)

Arguments

x	source data cube
expr	either a single string, or a vector of strings defining which reducers will be applied over which bands of the input cube
...	optional additional expressions (if expr is not a vector)
FUN	a user-defined R function applied over pixel time series (see Details)
names	character vector; if FUN is provided, names can be used to define the number and name of output bands

Details

Notice that expressions have a very simple format: the reducer is followed by the name of a band in parantheses. You cannot add more complex functions or arguments.

Possible reducers currently are "min", "max", "sum", "prod", "count", "mean", "median", "var", "sd".

Value

proxy data cube object

Note

Implemented reducers will ignore any NAN values (as na.rm=TRUE does).

This function returns a proxy object, i.e., it will not start any computations besides deriving the shape of the result.

Examples

# create image collection from example Landsat data only 
# if not already done in other examples
if (!file.exists(file.path(tempdir(), "L8.db"))) {
  L8_files <- list.files(system.file("L8NY18", package = "gdalcubes"),
                         ".TIF", recursive = TRUE, full.names = TRUE)
  create_image_collection(L8_files, "L8_L1TP", file.path(tempdir(), "L8.db"), quiet = TRUE) 
}

L8.col = image_collection(file.path(tempdir(), "L8.db"))
v = cube_view(extent=list(left=388941.2, right=766552.4, 
              bottom=4345299, top=4744931, t0="2018-01", t1="2018-12"),
              srs="EPSG:32618", nx = 497, ny=526, dt="P1M")
L8.cube = raster_cube(L8.col, v) 
L8.b02 = select_bands(L8.cube, c("B02"))
L8.b02.median = reduce_space(L8.b02, "median(B02)")  
L8.b02.median

plot(L8.b02.median)

gdalcubes documentation built on April 14, 2023, 5:08 p.m.