rrasterspatialnetcdfterra
How to convert a coarse raster to a smooth polygon
Say you have a raster, could be e.g. Sea Surface Temperature from NOAA with a grid: 0.25 degree latitude x 0.25 degree longitude global grid (1440x720).
Is it possible to convert a raster like this with R, so the output is smooth polygons? This would be an example from NYTimes where similar coarse raster files where somehow converted to 3 classes of smooth polygons.
Is there a clever way? I tried a lot with disaggregate, focal, reclassify, terra: aspolygons, smoothr:smooth
Nothing is really close to a smooth polygon. Any clues?
Here is a screenshot from the NYTimes 
Solution
Here is a possible work-flow. First go to a high spatial resolution with resample; make polygons; simplify.
library(terra)
x <- rast("filename")
x <- disagg(x, 10, method="bilinear")
# reclassify to get NA and one other value, e.g.
x <- ifel(x < 1, NA, 1)
p <- as.polygons(x)
s <- simplifyGeoms(p)
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