Extract zonal mean time series for an AOI

For each variable and period in the catalog, crops the COG to the AOI and computes the spatial mean per year (band). Returns a tidy tibble of raw climate values suitable for cd_baseline(), cd_anomaly(), or cd_trend().

Usage

cd_extract(
  catalog,
  aoi,
  variables = catalog$variable,
  periods = catalog$period,
  years = NULL,
  cache = TRUE
)

Arguments

catalog: A tibble from cd_catalog() with columns variable, period, href.
aoi: An sf or SpatVector polygon.
variables: Character vector of variables to extract. Defaults to all variables in catalog.
periods: Character vector of periods to extract. Defaults to all periods in catalog.
years: Optional integer vector to filter specific years.
cache: Logical. If TRUE (default), remote COGs are read through the on-disk cache (see cd_cache_fetch()) so repeated extractions and report rebuilds download each COG from S3 once rather than on every call. Passed through to cd_crop().

Value

A tibble with columns:

variable: Climate variable short name.
period: Temporal aggregation period.
year: Year (integer).
value: Spatial mean of the climate value for this AOI.

Examples

catalog <- cd_catalog(
  system.file("extdata", "example_catalog.json", package = "cd")
)
aoi <- sf::st_read(
  system.file("extdata", "example_aoi.gpkg", package = "cd"),
  quiet = TRUE
)
cd_extract(catalog, aoi)
#> # A tibble: 10 × 4
#>    variable period  year  value
#>    <chr>    <chr>  <int>  <dbl>
#>  1 tmean    annual  1951 -2.87 
#>  2 tmean    annual  1952 -2.01 
#>  3 tmean    annual  1953 -0.881
#>  4 tmean    annual  1954 -0.223
#>  5 tmean    annual  1955 -1.22 
#>  6 tmean    annual  1956 -2.88 
#>  7 tmean    annual  1957 -1.37 
#>  8 tmean    annual  1958 -1.34 
#>  9 tmean    annual  1959  0.537
#> 10 tmean    annual  1960 -1.61