R: Select a data cube band by name

gdalcubes_selection {gdalcubes} | R Documentation

## Select a data cube band by name

### Description

Select a data cube band by name

Extract a subset of a data cube

### Usage

    ## S3 method for class 'cube'
    x$name

    ## S3 method for class 'cube'
    cube[ib = TRUE, it = TRUE, iy = TRUE, ix = TRUE, ...]

### Arguments

`x` | source data cube
`name` | character; name of selected band
`cube` | source data cube
`ib` | first selector (optional), object of type character, list, Date, POSIXt, numeric, st_bbox), or st_sfc), see Details and examples
`it` | second selector (optional), see `ib`
`iy` | third selector (optional), see `ib`
`ix` | fourth selector (optional), see `ib`
`...` | further arguments, not used

### Details

The `[]` operator allows for flexible subsetting of data cubes by date, datetime, bounding box, spatial points, and band names. Depending on the arguments, it supports slicing ( selecting one element of a dimension) and cropping (selecting a subinterval of a dimension) and combinations thereof (e.g., selecting a spatial window and a temporal slice). Dimension subsets can be specified by integer indexes or coordinates / datetime values. Arguments are matched by type and order. For example, if the first argument is a length-two vector of type Date, the function will realize that this is for subsetting the time dimension. If needed, arguments are treated in the order band, time, y, x.

### Note

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

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"))
    }
    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="P3M", aggregation = "median")
    L8.cube = raster_cube(L8.col, v, mask=image_mask("BQA", bits=4, values=16))
    L8.red = L8.cube$B04

    plot(L8.red)

    # 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"))
    }
    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="2018-01-01", t1="2018-12-31"),
                  srs="EPSG:32618", nx = 497, ny=526, dt="P1D", aggregation = "median")
    L8.cube = raster_cube(L8.col, v, mask=image_mask("BQA", bits=4, values=16))

    L8.cube[c("B05","B04")] # select bands
    L8.cube[as.Date(c("2018-01-10", "2018-01-20"))] # crop by time
    L8.cube[as.Date("2018-01-10")] # slice by time
    L8.cube["B05", "2018-01-10"] # select bands and slice by time
    L8.cube["B05", c("2018-01-10","2018-01-17")] # select bands and crop by time
    L8.cube[, c("2018-01-10","2018-01-17")] # crop by time

    # crop by space (coordinates and integer indexes respectively)
    L8.cube[list(left=388941.2 + 1e5, right=766552.4 - 1e5, bottom=4345299 + 1e5, top=4744931 - 1e5)]
    L8.cube[,,c(1,100), c(1,100)]

    L8.cube[,c(1,2),,] # crop by time (integer indexes)

    # select by spatial point or bounding box
    if (requireNamespace("sf", quietly = TRUE)) {
      s = sf::st_sfc(sf::st_point(c(500000, 4500000)), crs = "EPSG:32618")
      L8.cube[s]

      bbox =  sf::st_bbox(c(xmin = 388941.2 + 1e5, xmax = 766552.4 - 1e5,
                       ymax = 4744931 - 1e5, ymin = 4345299 + 1e5), crs = sf::st_crs(32618))
      L8.cube[bbox]
    }

[Package gdalcubes version 0.6.0 Index]