rgee (version 0.2.0)

ee_extract: Extract values from Earth Engine Images or ImageCollections objects

Description

Extract values from a Image or ImageCollection spatial object at the locations of a geometry object. You can use ee.Geometries, ee.Features, ee.FeatureCollection and sf objects.

Usage

ee_extract(x, y, fun = ee$Reducer$mean(), scale = 1000, id = NULL,
  ...)

Arguments

x

ee$Image or ee$ImageCollection.

y

ee$Geometry, ee$Feature, ee$FeatureCollection or sf objects.

fun

ee$Reducer object. Function to summarize the values. See details.

scale

A nominal scale in meters of the projection to work in.

id

Character. Name of the column to be used as a geometry index.

...

reduceRegions additional parameters. See reticulate::ee_help(ee$Image()$reduceRegions) for more details.

Details

The fun arguments just admit Reducer objects that return one value. These are:

• allNonZero: Returns a Reducer that returns 1 if all of its inputs are non-zero, 0 otherwise.

• anyNonZero: Returns a Reducer that returns 1 if any of its inputs are non-zero, 0 otherwise.

• bitwiseAnd: Returns a Reducer that computes the bitwise-and summation of its inputs.

• bitwiseOr: Returns a Reducer that computes the bitwise-or summation of its inputs.

• count: Returns a Reducer that computes the number of non-null inputs.

• first: Returns a Reducer that returns the first of its inputs.

• firstNonNull: Returns a Reducer that returns the first of its non-null inputs.

• kurtosis: Returns a Reducer that Computes the kurtosis of its inputs.

• last: Returns a Reducer that returns the last of its inputs.

• lastNonNull: Returns a Reducer that returns the last of its non-null inputs.

• max: Creates a reducer that outputs the maximum value of its (first) input. If numInputs is greater than one, also outputs the corresponding values of the additional inputs.

• mean: Returns a Reducer that computes the (weighted) arithmetic mean of its inputs.

• median: Create a reducer that will compute the median of the inputs. For small numbers of inputs (up to maxRaw) the median will be computed directly; for larger numbers of inputs the median will be derived from a histogram.

• min: Creates a reducer that outputs the minimum value of its (first) input. If numInputs is greater than one, also outputs additional inputs.

• mode: Create a reducer that will compute the mode of the inputs. For small numbers of inputs (up to maxRaw) the mode will be computed directly; for larger numbers of inputs the mode will be derived from a histogram.

• product: Returns a Reducer that computes the product of its inputs.

• sampleStdDev: Returns a Reducer that computes the sample standard deviation of its inputs.

• sampleVariance: Returns a Reducer that computes the sample variance of its inputs.

• stdDev: Returns a Reducer that computes the standard deviation of its inputs.

• sum: Returns a Reducer that computes the (weighted) sum of its inputs.

• variance: Returns a Reducer that computes the variance of its inputs.

Examples

# NOT RUN {
library(rgee)
library(sf)

ee_reattach() # reattach ee as a reserved word
ee_Initialize()

# get monthly precipitation from terraclimate
terraclimate <- ee$ImageCollection("IDAHO_EPSCOR/TERRACLIMATE")$
  filterDate("2000-01-01", "2001-01-01")$
  map(function(x) x$select("pr"))

# extract values with polygons
nc <- st_read(system.file("shape/nc.shp", package = "sf"), quiet = TRUE) %>%
  st_transform(4326)
ee_nc_rain <- ee_extract(
  x = terraclimate, y = nc, fun = ee$Reducer$max(),
  id = "FIPS"
)
ee_nc_rain <- merge(nc, ee_nc_rain, by = "FIPS")
plot(ee_nc_rain["X200006"],
  main = "2001 Jan Precipitation - Terraclimate",
  reset = FALSE
)

## plot time series
ee_nc <- ee_nc_rain
st_geometry(ee_nc) <- NULL
time_serie <- as.numeric(ee_nc[1, sprintf("X%s", 200001:200012)])
main <- sprintf("2001 Precipitation - %s", ee_nc$NAME[1])
plot(time_serie, ylab = "pp (mm/month)", type = "l", lwd = 1.5, main = main)
points(time_serie, pch = 20, lwd = 1.5, cex = 1.5)
# }