Query a datacube

These functions query a datacube to which a connection has been established using database_connect.

dc_close(dc = getOption("odcr.dc"))

dc_find_datasets(dc = getOption("odcr.dc"), query, lazy = FALSE)

dc_list_measurements(dc = getOption("odcr.dc"))

dc_list_products(dc = getOption("odcr.dc"))

dc_load(dc = getOption("odcr.dc"), query)

Arguments

dc	a datacube connection of class 'datacube.api.core.Datacube'. By default, the session connection initialized using connect() is used.
query	list, containing query parameters such as 'product', character, name of the product to be queries (see dc_list_products()) 'time', character vector of length == 2, containing a time query 'x', numeric vector of length == 2, containing xmin and xmax 'y', numeric vector of length == 2, containing ymin and ymax 'output_crs', character, the output CRS, e.g. as epsg in the format 'epsg:6933' 'resolution', numeric vector of length == 2 'measurements', character vector containing the names or aliases of measurements
lazy	logical, whether to use lazy dataset finding or not.

Value

None or data.frame

Examples

if (FALSE) {
library(odcr)

# connect to a database
database_connect(app = "Sentinel_2")

# return a data.frame containing all stored variables/measurements of the current connection
# and its aliases, data types etc.
dc_list_measurements()

# return a data.frame containing all products of the current connection
dc_list_products()

# build a query list
lat <- 22.821
lon <- 28.518
buffer <- 0.05

query <- list(
  'time' = c('2020-01', '2020-03'),
  'x' = c(lon - buffer, lon + buffer),
  'y' = c(lat + buffer, lat - buffer),
  'output_crs' = 'epsg:6933',
  'resolution' = c(-20,20)
)

# return a data.frame of all datasets matching the query
dc_find_datasets(query = c(product = "s2_l2a", query))

# load data and return an xarray object for a query
ds <- dc_load(query = c(product = "s2_l2a", dask_chunks = dict(), query))

# after a lot of queries, you may want to close open connections
dc_close()
}