starsExtra (version 0.2.8)

extract2: Extract raster values by lines or polygons

Description

Extract raster values by lines or polygons, summarizing for each feature using a function specified by the user. This function is aimed to reproduce (some of) the functionality of raster::extract.

Usage

extract2(x, v, fun, progress = TRUE, ...)

Value

A vector (single-band raster) or matrix (multi-band raster) with the extracted and summarized values

Arguments

x

A stars object

v

An sf layer that determines values to extract

fun

A function to summarize cell values per feature/band

progress

Display progress bar? The default is TRUE

...

Further arguments passed to fun

Examples

# Polygons
pol = st_bbox(landsat)
pol = st_as_sfc(pol)
set.seed(1)
pol = st_sample(pol, 5)
pol = st_buffer(pol, 100)
pol = c(pol, pol)

# Plot
plot(landsat[,,,1,drop=TRUE], reset = FALSE)
plot(pol, add = TRUE)

# Single-band raster
aggregate(landsat[,,,1,drop=TRUE], pol, mean, na.rm = TRUE)[[1]]  ## Duplicated areas get 'NA'
extract2(landsat[,,,1,drop=TRUE], pol, mean, na.rm = TRUE, progress = FALSE)

# Multi-band example
extract2(landsat, pol, mean, na.rm = TRUE, progress = FALSE)

# Lines
lines = st_cast(pol, "LINESTRING")

# Single-band raster
extract2(landsat[,,,1,drop=TRUE], lines, mean, na.rm = TRUE, progress = FALSE)

# Multi-band example
extract2(landsat, lines, mean, na.rm = TRUE, progress = FALSE)