addVarEEclosestImage: Add variable from closest image ina Google Earth Engine...

In AfricaBirdData/ABAP: Access to African Bird Atlas Project data from R

Add variable from closest image ina Google Earth Engine Collection

Description

Each feature in a feature collection (i.e. row in asimple feature collection) is matched with the image in an image collection that is closest to it in time.

Usage

addVarEEclosestImage(
  ee_pentads,
  collection,
  reducer,
  maxdiff,
  bands = NULL,
  unmask = FALSE
)

Arguments

ee_pentads	A feature collection with the pentads we want to annotate. We need to upload an sf object with the pentads to GEE. This object must also have character column with the dates that need to be matched against the image collection dates. The format must be "yyyy-mm-dd" and the column must be named "Date".
collection	Either a character string with the name of the collection we want to use or a GEE collection produced with ee$ImageCollection(). See GEE catalog.
reducer	A character string specifying the function apply when extracting values for each pentad. It is common to use "mean", "sum" or "count". But there are many other, see 'ee.Reducer' under Client Libraries at https://developers.google.com/earth-engine/apidocs.
maxdiff	Maximum difference in days allowed for an image to be matched with data.
bands	Select specific bands from the image. Only one band at a time is allowed for now.
unmask	GEE masks missing values, which means they are not used for computing means, counts, etc. Sometimes we might want to avoid this behaviour and use 0 instead of NA. If so, set unmask to TRUE.

Value

A dataframe similar to ee_pentads with variables added from the bands selected from collection. Note that following rgee the name of the new variables will be the selected band (bands or else all bands from collection followed by the spatial reducer reducer.

Examples

## Not run: 
# Load the remote data asset
ee_data <- ee$FeatureCollection(assetId)  # assetId must correspond to an asset in your GEE account

# Annotate with TerraClimate dataset
visit_new <- addVarEEclosestImage(ee_pentads = ee_data,
                                  collection = "IDAHO_EPSCOR/TERRACLIMATE",
                                  reducer = "mean",                          # We only need spatial reducer
                                  maxdiff = 15,                              # This is the maximum time difference that GEE checks
                                  bands = c("tmmn"))

## End(Not run)

AfricaBirdData/ABAP documentation built on Aug. 4, 2024, 4:41 p.m.