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65 lines
2 KiB
R
65 lines
2 KiB
R
% Generated by roxygen2: do not edit by hand
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% Please edit documentation in R/apply_time.R
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\name{apply_time}
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\alias{apply_time}
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\title{Apply a function over (multi-band) pixel time series}
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\usage{
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apply_time(x, ...)
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}
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\arguments{
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\item{x}{input data}
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\item{...}{additional arguments passed to method implementations}
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}
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\value{
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return value and type depend on the class of x
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}
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\description{
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This generic function applies a function on pixel time series of a data cube, an R array, or other classes if implemented.
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The resulting object is expected to have the same spatial and temporal shape as the input, i.e., no reduction is performed.
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}
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\examples{
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# 1. input is data cube
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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="2018-06"),
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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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L8.ndvi = apply_pixel(L8.cube, "(B05-B04)/(B05+B04)", "NDVI")
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# Apply a user defined R function
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apply_time(L8.ndvi, names="NDVI_residuals",
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FUN=function(x) {
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y = x["NDVI",]
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if (sum(is.finite(y)) < 3) {
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return(rep(NA,ncol(x)))
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}
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t = 1:ncol(x)
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return(predict(lm(y ~ t)) - x["NDVI",])})
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# 2. input is array
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d <- c(4,16,32,32)
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x <- array(rnorm(prod(d)), d)
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z <- apply_time(x, function(v) {
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y = matrix(NA, ncol=ncol(v), nrow=2)
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y[1,] = (v[1,] + v[2,]) / 2
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y[2,] = (v[3,] + v[4,]) / 2
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y
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})
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dim(z)
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}
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\seealso{
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\code{\link{apply_time.cube}}
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\code{\link{apply_time.array}}
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}
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