Extract values for a Image or ImageCollection spatial object at the locations of geometry object. You can use ee.Geometries, ee.Features, ee.FeatureCollection and sf objects.
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 aditional parameters. See ee_help(ee$Image()$reduceRegions) for 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 the corresponding values of the 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
library(rgee) library(sf) ee_Initialize() terraclimate <- ee$ImageCollection("IDAHO_EPSCOR/TERRACLIMATE")$ filterDate("2000-01-01", "2001-01-01")$ map(function(x) x$select("pr")) nc <- st_read(system.file("shape/nc.shp", package = "sf"), quiet = TRUE) %>% st_transform(4326) # all(!nc$FIPS %in% nc$FIPS[duplicated(nc$FIPS)]) -- Unique ID? 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)## time series dev.off()#> null device #> 1ee_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)
