rgee (version 1.0.8)

ee_extract: Extract values from EE Images or ImageCollections objects

Description

Extract values from a ee$Image at the locations of a geometry object. You can use ee$Geometry$*, ee$Feature, ee$FeatureCollection, sf or sfc objects. This function mimicking how extract currently works.

Usage

ee_extract(
  x,
  y,
  fun = ee$Reducer$mean(),
  scale = NULL,
  sf = FALSE,
  quiet = FALSE,
  ...
)

Arguments

x

ee$Image.

y

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

fun

ee$Reducer object. Function to summarize the values. The function must take a single numeric value as an argument and return a single value. See details.

scale

A nominal scale in meters of the Image projection to work in. By default 1000.

sf

Logical. Should return a sf object?

quiet

Logical. Suppress info message.

...

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

Value

A data.frame or an sf object depending on the sf argument. Column names are extracted from band names, use ee$Image$rename to rename the bands of an ee$Image. See ee_help(ee$Image$rename).

Details

The reducer functions that return one value 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_Initialize()

# Define a Image or ImageCollection: Terraclimate
terraclimate <- ee$ImageCollection("IDAHO_EPSCOR/TERRACLIMATE") %>%
  ee$ImageCollection$filterDate("2001-01-01", "2002-01-01") %>%
  ee$ImageCollection$map(
    function(x) {
      date <- ee$Date(x$get("system:time_start"))$format('YYYY_MM_dd')
      name <- ee$String$cat("Terraclimate_pp_", date)
      x$select("pr")$rename(name)
    }
  )

# Define a geometry
nc <- st_read(
  dsn = system.file("shape/nc.shp", package = "sf"),
  stringsAsFactors = FALSE,
  quiet = TRUE
)


# Extract values

ee_nc_rain <- ee_extract(
  x = terraclimate,
  y = nc,
  scale = 250,
  fun = ee$Reducer$mean(),
  sf = TRUE
)

# Spatial plot
plot(
  ee_nc_rain["Terraclimate_pp_2001_11_01"],
  main = "2001 Jan Precipitation - Terraclimate",
  reset = FALSE
)
# }