Warp (resample) grids in stars objects to a new grid, possibly in an new coordinate reference system

  crs = NA_crs_,
  cellsize = NA_real_,
  segments = 100,
  use_gdal = FALSE,
  options = character(0),
  no_data_value = NA_real_,
  debug = FALSE,
  method = "near"



object of class stars with source raster


object of class stars with target raster geometry




coordinate reference system for destination grid, only used when dest is missing


length 1 or 2 numeric; cellsize in target coordinate reference system units


(total) number of segments for segmentizing the bounding box before transforming to the new crs


logical; if TRUE, use gdalwarp, through gdal_utils


character vector with options, passed on to gdalwarp


value used by gdalwarp for no_data (NA) when writing to temporary file


logical; if TRUE, do not remove the temporary gdalwarp destination file, and print its name


character; see details for options; methods other than near only work when use_gdal=TRUE


method should be one of near, bilinear, cubic, cubicspline, lanczos, average, mode, max, min, med, q1 or q3; see https://github.com/r-spatial/stars/issues/109

For gridded spatial data (dimensions x and y), see figure; the existing grid is transformed into a regular grid defined by dest, possibly in a new coordinate reference system. If dest is not specified, but crs is, the procedure used to choose a target grid is similar to that of projectRaster (currently only with method='ngb'). This entails: (i) the envelope (bounding box polygon) is transformed into the new crs, possibly after segmentation (red box); (ii) a grid is formed in this new crs, touching the transformed envelope on its East and North side, with (if cellsize is not given) a cellsize similar to the cell size of src, with an extent that at least covers x; (iii) for each cell center of this new grid, the matching grid cell of x is used; if there is no match, an NA value is used.


geomatrix = system.file("tif/geomatrix.tif", package = "stars") (x = read_stars(geomatrix))
#> stars object with 2 dimensions and 1 attribute #> attribute(s): #> geomatrix.tif #> Min. : 74.0 #> 1st Qu.:107.0 #> Median :123.0 #> Mean :126.8 #> 3rd Qu.:132.0 #> Max. :255.0 #> dimension(s): #> from to offset delta refsys point values x/y #> x 1 20 1841002 1.5 PROJCS["WGS 84 / UTM zone... TRUE NULL [x] #> y 1 20 1144003 -1.5 PROJCS["WGS 84 / UTM zone... TRUE NULL [y] #> sheared raster with parameters: -5 -5
new_crs = st_crs(4326) y = st_warp(x, crs = new_crs) plot(st_transform(st_as_sfc(st_bbox(x)), new_crs), col = NA, border = 'red')
plot(st_as_sfc(y, as_points=FALSE), col = NA, border = 'green', axes = TRUE, add = TRUE)
image(y, add = TRUE, nbreaks = 6)
plot(st_as_sfc(y, as_points=TRUE), pch=3, cex=.5, col = 'blue', add = TRUE)
plot(st_transform(st_as_sfc(x, as_points=FALSE), new_crs), add = TRUE)
# warp 0-360 raster to -180-180 raster: r = read_stars(system.file("nc/reduced.nc", package = "stars"))
#> sst, anom, err, ice,
r %>% st_set_crs(4326) %>% st_warp(st_as_stars(st_bbox(), dx = 2)) -> s plot(r, axes = TRUE) # no CRS set, so no degree symbols in labels
plot(s, axes = TRUE)