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48 lines
1.8 KiB
R
48 lines
1.8 KiB
R
% Generated by roxygen2: do not edit by hand
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% Please edit documentation in R/streaming.R
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\name{write_chunk_from_array}
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\alias{write_chunk_from_array}
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\title{Write chunk data of a cube to stdout or a file}
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\usage{
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write_chunk_from_array(v)
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}
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\arguments{
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\item{v}{four-dimensional array with dimensions band, time, y, and x}
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}
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\description{
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This function can be used within function passed to \code{\link{chunk_apply}} in order to pass four-dimensional R arrays as a
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data cube chunk to the gdalcubes C++ library. It works only for R processes, which have been started from the gdalcubes C++ library.
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The input array must have dimensions band, time, y, x (in this order).
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}
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\note{
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Call this function ONLY from a function passed to \code{\link{chunk_apply}}.
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This function only works in R sessions started from gdalcubes streaming.
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}
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\examples{
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\donttest{
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# create image collection from example Landsat data only
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# if not already done in other examples
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if (!file.exists(file.path(tempdir(), "L8.db"))) {
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L8_files <- list.files(system.file("L8NY18", package = "gdalcubes"),
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".TIF", recursive = TRUE, full.names = TRUE)
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create_image_collection(L8_files, "L8_L1TP", file.path(tempdir(), "L8.db"), quiet = TRUE)
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}
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L8.col = image_collection(file.path(tempdir(), "L8.db"))
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v = cube_view(extent=list(left=388941.2, right=766552.4,
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bottom=4345299, top=4744931, t0="2018-01", t1="2018-12"),
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srs="EPSG:32618", nx = 497, ny=526, dt="P1M")
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L8.cube = raster_cube(L8.col, v)
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L8.cube = select_bands(L8.cube, c("B04", "B05"))
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f <- function() {
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x <- read_chunk_as_array()
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out <- reduce_time(x, function(x) {
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cor(x[1,], x[2,], use="na.or.complete", method = "kendall")
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})
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write_chunk_from_array(out)
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}
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L8.cor = chunk_apply(L8.cube, f)
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plot(L8.cor, zlim=c(0,1), key.pos=1)
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}
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}
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